phase 11: plumbing prereqs — Wiki, edits, config, snapshot, diags

Cross-cutting infrastructure that every v1.1 phase depends on. Lands as
a numbered phase before any user-visible feature so Phases 12–19 stay
mechanical.

5 pieces:

- `config.rs` — `Config` + `WikiConfig` + `DiagnosticConfig` + `LinkSeverity`.
  Serde-deserialised from `initialization_options`. v1.0 single-wiki
  shape (`wiki_root` + `file_extension` + `syntax`) desugars to one-entry
  `wikis = [...]` per P16. `~/...` expansion without pulling in `dirs`.
  Fallbacks: workspace_folders[0] → deprecated root_uri → empty list.

- `wiki.rs` — `Wiki` aggregate (id + WikiConfig + Arc<RwLock<Index>>).
  `build_wikis(&[WikiConfig])` materialises the list; `resolve_uri_to_wiki`
  picks the longest-prefix root match so nested wikis route correctly.
  Single-entry today, multi-entry once Phase 18 lands.

- `edits.rs` — `WorkspaceEditBuilder` + `text_edit_replace/insert/delete`
  + `op_rename/delete/create`. Handles the UTF-8/UTF-16 conversion at the
  span boundary so each Phase 13+ command stays a 3-liner. Builder picks
  `documentChanges` when file ops are present (LSP requires it), `changes`
  map otherwise (works for LSP 3.15- clients). File ops precede content
  edits in the output so created/renamed files exist when edits apply.
  `DeleteFile` is built without `annotation_id` — lsp-types 0.94.x ships
  it that way; later versions added the field.

- `Backend` refactor — `index: Arc<RwLock<WorkspaceIndex>>` replaced by
  `wikis: Arc<RwLock<Vec<Wiki>>>` + `config: Arc<RwLock<Config>>`. New
  `wiki(id)` / `default_wiki()` / `wiki_for_uri(uri)` helpers. Every v1.0
  handler (definition, references, hover, completion, workspace/symbol,
  update_document) goes through `wiki_for_uri`. `initialize` builds wikis
  from `Config::from_init_params`; `initialized` spawns one indexer task
  per wiki with the existing `window/workDoneProgress` wrapper. New
  `did_change_configuration` handler re-applies settings (rebuild
  semantics revisited in Phase 18). The old `workspace_root_from_params`
  helper is gone.

- `read_or_open` + `DocSnapshot` (scaffolded, `#[allow(dead_code)]` until
  Phase 13's `workspace/rename` consumes it). Returns the live document
  when held in the documents map, otherwise async-reads from disk and
  re-parses so cross-document operations get accurate text and spans
  instead of trusting stale `WorkspaceIndex` data.

- `collect_diagnostics` composable collector. Same `ErrorNode` walk
  today; takes `Option<&WorkspaceIndex>` + `page_name` + `&DiagnosticConfig`
  so Phase 15 can drop a link-health source in without further refactor.
  `ast_diagnostics` kept as a thin wrapper for the v1.0 test surface.

New deps: `serde` + `serde_json` (already transitive through tower-lsp;
elevated to direct deps for clarity and stability). `tokio` gains the
`fs` feature for `read_or_open`'s async disk read.

Tests (19 new in `phase11_plumbing.rs`):
- Edits: UTF-8 passthrough + UTF-16 conversion (`héllo`), insert/delete
  shape, builder mode selection, file-op accumulation, `op_create` round-trip
- Config: defaults, v1.0 desugar, explicit list overrides legacy, empty
  JSON, invalid JSON preserves prior state
- Wiki: sequential id assignment, longest-prefix resolution, no-match,
  `Wiki::contains`
- Diagnostics: error-node composition, link-health stub returns empty in
  Phase 11

All 172 v1.0 tests still pass — backward compatible.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

crates/nuwiki-lsp/src/config.rs

@@ -0,0 +1,216 @@
+//! Server-side runtime config.
+//!
+//! Populated from `InitializeParams.initialization_options` at boot and
+//! refreshed via `workspace/didChangeConfiguration` (P18). v1.0 single-wiki
+//! shapes are accepted and desugared into the v1.1 `wikis = [...]` form so
+//! existing setups keep working (P16).
+//!
+//! Only the fields actually consumed in Phase 11 land here. Phases 13–19
+//! extend `WikiConfig` (diary path, html path, template options, …) and
+//! the top-level `Config` (diagnostic severity, mappings opt-in, …) as
+//! they need them.
+
+use std::path::{Path, PathBuf};
+
+use serde::Deserialize;
+use tower_lsp::lsp_types::{InitializeParams, Url};
+
+#[derive(Debug, Clone, Default)]
+pub struct Config {
+    pub wikis: Vec<WikiConfig>,
+    pub diagnostic: DiagnosticConfig,
+}
+
+#[derive(Debug, Clone)]
+pub struct WikiConfig {
+    pub name: String,
+    pub root: PathBuf,
+    pub file_extension: String,
+    pub syntax: String,
+}
+
+#[derive(Debug, Clone, Default)]
+pub struct DiagnosticConfig {
+    pub link_severity: LinkSeverity,
+}
+
+#[derive(Debug, Clone, Copy, Default, PartialEq, Eq)]
+pub enum LinkSeverity {
+    Off,
+    Hint,
+    #[default]
+    Warning,
+    Error,
+}
+
+impl WikiConfig {
+    /// Synthetic default used when the client supplies neither
+    /// `initializationOptions` nor a workspace root. `name` is empty;
+    /// callers shouldn't depend on it for routing.
+    pub fn empty() -> Self {
+        Self {
+            name: String::new(),
+            root: PathBuf::new(),
+            file_extension: ".wiki".into(),
+            syntax: "vimwiki".into(),
+        }
+    }
+
+    pub fn from_root(root: PathBuf) -> Self {
+        Self {
+            name: root
+                .file_name()
+                .map(|s| s.to_string_lossy().into_owned())
+                .unwrap_or_default(),
+            root,
+            file_extension: ".wiki".into(),
+            syntax: "vimwiki".into(),
+        }
+    }
+}
+
+impl Config {
+    /// Build a `Config` from `InitializeParams`.
+    ///
+    /// Priority for the wikis list:
+    ///   1. `initialization_options.wikis = [...]` (v1.1 shape)
+    ///   2. `initialization_options.wiki_root + file_extension + syntax`
+    ///      (v1.0 single-wiki shape, P16)
+    ///   3. `workspace_folders[0]` if present
+    ///   4. deprecated `root_uri` if present
+    ///   5. empty list (server stays alive but won't index anything)
+    pub fn from_init_params(params: &InitializeParams) -> Self {
+        let raw = params
+            .initialization_options
+            .as_ref()
+            .and_then(|v| serde_json::from_value::<InitOptions>(v.clone()).ok())
+            .unwrap_or_default();
+
+        let wikis = if let Some(list) = raw.wikis {
+            list.into_iter().map(WikiConfig::from).collect()
+        } else if let Some(root) = raw.wiki_root.as_deref().and_then(expand_path) {
+            vec![WikiConfig {
+                name: root
+                    .file_name()
+                    .map(|s| s.to_string_lossy().into_owned())
+                    .unwrap_or_default(),
+                root,
+                file_extension: raw.file_extension.unwrap_or_else(|| ".wiki".into()),
+                syntax: raw.syntax.unwrap_or_else(|| "vimwiki".into()),
+            }]
+        } else if let Some(folder) = first_workspace_folder(params) {
+            vec![WikiConfig::from_root(folder)]
+        } else {
+            Vec::new()
+        };
+
+        Config {
+            wikis,
+            diagnostic: DiagnosticConfig::default(),
+        }
+    }
+
+    /// Re-apply settings received via `workspace/didChangeConfiguration`.
+    /// On parse failure the existing config is returned unchanged.
+    pub fn apply_change(&mut self, value: &serde_json::Value) {
+        let raw: InitOptions = match serde_json::from_value(value.clone()) {
+            Ok(r) => r,
+            Err(_) => return,
+        };
+        if let Some(list) = raw.wikis {
+            self.wikis = list.into_iter().map(WikiConfig::from).collect();
+        } else if let Some(root) = raw.wiki_root.as_deref().and_then(expand_path) {
+            let mut wc = WikiConfig::from_root(root);
+            if let Some(ext) = raw.file_extension {
+                wc.file_extension = ext;
+            }
+            if let Some(s) = raw.syntax {
+                wc.syntax = s;
+            }
+            self.wikis = vec![wc];
+        }
+    }
+}
+
+// ===== Wire schema =====
+
+#[derive(Debug, Default, Deserialize)]
+#[serde(default, rename_all = "snake_case")]
+struct InitOptions {
+    wikis: Option<Vec<RawWiki>>,
+    // v1.0 single-wiki compat fields
+    wiki_root: Option<String>,
+    file_extension: Option<String>,
+    syntax: Option<String>,
+    log_level: Option<String>,
+}
+
+#[derive(Debug, Deserialize)]
+#[serde(rename_all = "snake_case")]
+struct RawWiki {
+    #[serde(default)]
+    name: Option<String>,
+    root: String,
+    #[serde(default)]
+    file_extension: Option<String>,
+    #[serde(default)]
+    syntax: Option<String>,
+}
+
+impl From<RawWiki> for WikiConfig {
+    fn from(r: RawWiki) -> Self {
+        let root = expand_path(&r.root).unwrap_or_default();
+        let derived_name = root
+            .file_name()
+            .map(|s| s.to_string_lossy().into_owned())
+            .unwrap_or_default();
+        WikiConfig {
+            name: r.name.unwrap_or(derived_name),
+            root,
+            file_extension: r.file_extension.unwrap_or_else(|| ".wiki".into()),
+            syntax: r.syntax.unwrap_or_else(|| "vimwiki".into()),
+        }
+    }
+}
+
+fn expand_path(s: &str) -> Option<PathBuf> {
+    let trimmed = s.trim();
+    if trimmed.is_empty() {
+        return None;
+    }
+    // Best-effort `~` expansion. Avoids pulling in `dirs` or `home`.
+    if let Some(rest) = trimmed.strip_prefix("~/") {
+        if let Some(home) = std::env::var_os("HOME") {
+            return Some(Path::new(&home).join(rest));
+        }
+    } else if trimmed == "~" {
+        if let Some(home) = std::env::var_os("HOME") {
+            return Some(PathBuf::from(home));
+        }
+    }
+    Some(PathBuf::from(trimmed))
+}
+
+fn first_workspace_folder(params: &InitializeParams) -> Option<PathBuf> {
+    if let Some(folders) = &params.workspace_folders {
+        if let Some(first) = folders.first() {
+            return first.uri.to_file_path().ok();
+        }
+    }
+    #[allow(deprecated)]
+    if let Some(uri) = &params.root_uri {
+        return uri.to_file_path().ok();
+    }
+    None
+}
+
+/// Test helper: build a `Config` from a JSON value (mimics what arrives
+/// in `initializationOptions`).
+pub fn config_from_json(value: serde_json::Value) -> Config {
+    let mut cfg = Config::default();
+    cfg.apply_change(&value);
+    cfg
+}
+
+#[allow(dead_code)]
+fn _ensure_url_is_used(_u: &Url) {}