fix(mcp): resolve module-qualified symbol lookups (#173) (#179)

`codegraph_callees stage_apply::run` (and `_node`, `_impact`, ...)
returned "not found" against a repo with 7-9 sibling Rust modules,
each exporting `pub async fn run`. Two underlying issues:

1. The FTS5 query builder stripped `:` as a special char without
   splitting on `::`, so `stage_apply::run` collapsed to the literal
   `stage_applyrun` which matches nothing. Treat `::` as whitespace
   before the strip step so both halves become FTS tokens.

2. `matchesSymbol` only understood `Parent.child` qualifiers and
   relied on `qualifiedName` carrying the module path. Rust file-
   level functions don't have their module name in `qualifiedName`
   (it's encoded in the file path instead), so even dot-style
   lookups failed. Accept `::`, `.`, `/` as separators; multi-level
   forms compose; Rust `crate::`/`super::`/`self::` prefixes get
   stripped before path matching. Fall back to file-path containment
   when the qualified-name suffix doesn't match — `stage_apply::run`
   matches a `run` in any file whose path has a `stage_apply` segment.

Also tightens the no-match branch: qualified lookups no longer fall
through to a fuzzy text match. `stage_apply::nonexistent_fn` returns
`null` instead of silently resolving to an unrelated `rollback` in
the same file.

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

CHANGELOG.md

@@ -37,6 +37,29 @@ and adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0.html).
   [#168](https://github.com/colbymchenry/codegraph/issues/168). Thanks to
   [@starkleek](https://github.com/starkleek) for the report and to
   [@Bortlesboat](https://github.com/Bortlesboat) for the initial PR.
+- **MCP / search**: module-qualified symbol lookups now resolve. The
+  MCP tools (`codegraph_node`, `codegraph_callees`, `codegraph_impact`,
+  …) accept `module::symbol` (Rust / C++ / Ruby), `Module.symbol`
+  (TS / JS / Python), and `module/symbol` (path-style) — multi-level
+  forms (`crate::configurator::stage_apply::run`) and Rust path
+  prefixes (`crate`, `super`, `self`) are handled. Two underlying
+  fixes:
+    - The FTS5 query builder now treats `::` as a token separator
+      instead of stripping it to nothing, so `stage_apply::run` no
+      longer collapses to the unsearchable `stage_applyrun`.
+    - `matchesSymbol` falls back to a file-path containment check when
+      `qualifiedName` doesn't carry the module hierarchy (Rust file-
+      level functions, Python free functions in a package): a `run`
+      in `src/configurator/stage_apply.rs` now matches
+      `stage_apply::run` because `stage_apply` appears as a path
+      segment.
+    - Qualified lookups that don't match the qualifier no longer fall
+      through to fuzzy text matches — `stage_apply::nonexistent_fn`
+      returns `null` instead of resolving to an unrelated `rollback`
+      in the same file.
+  Closes [#173](https://github.com/colbymchenry/codegraph/issues/173).
+  Thanks to [@joselhurtado](https://github.com/joselhurtado) for the
+  detailed reproduction.
 
 [0.7.10]: https://github.com/colbymchenry/codegraph/releases/tag/v0.7.10