feat(native): port Clojure extractor to Rust (#1097)

* feat(native): port Clojure extractor to Rust

Adds tree-sitter-clojure dependency and native extractor matching
the WASM-side behavior for Clojure symbol, import, and call extraction.

Part of #1071

* fix(native): harden clojure extractor child iteration and document parity gaps

Address Greptile review feedback on PR #1097:

- `find_first_symbol`/`find_second_symbol`: replace `?` with `match` so a
  `None` from `list_node.child(i)` skips and continues instead of aborting
  the whole scan, matching the JS extractor's `if (!child) continue;`
  semantics. Practically inert today (tree-sitter always returns `Some`
  for `i < child_count()`), but makes the invariant explicit and removes
  a fragile divergence.
- `extract_clojure_params`: document the known `defmethod` dispatch-vector
  gap inherited from the JS extractor.
- `handle_import_form`: document why top-level `(require 'some.ns)` and
  `(require '[some.ns :as s])` are silently dropped and point maintainers
  at the working `(ns ...)` path in `extract_ns_requires`.

Author: carlos-alm

Cargo.lock

@@ -35,6 +35,7 @@ tree-sitter-dart = "0.0.4"
 tree-sitter-zig = "1"
 tree-sitter-haskell = "0.23"
 tree-sitter-ocaml = "0.24"
+tree-sitter-clojure-orchard = "0.2"
 rayon = "1"
 ignore = "0.4"
 globset = "0.4"

crates/codegraph-core/Cargo.toml

@@ -132,7 +132,7 @@ fn load_file_hashes(conn: &Connection) -> Option<HashMap<String, FileHashRow>> {
 /// found on disk are treated as removed.
 ///
 /// Files whose extension is outside the Rust file_collector's supported set
-/// (e.g. `.clj`, `.gleam`, `.jl`, `.fs` — WASM-only languages) are skipped:
+/// (e.g. `.gleam`, `.jl`, `.fs` — WASM-only languages) are skipped:
 /// the orchestrator's narrower collector never sees them, so absence from
 /// `current` is a capability boundary, not a deletion. Their `nodes` and
 /// `file_hashes` rows are owned by the JS-side WASM backfill (#967, #1068)
@@ -774,14 +774,13 @@ mod tests {
 
     #[test]
     fn detect_removed_skips_unsupported_extensions() {
-        // Files in WASM-only languages (Clojure, Gleam, Julia, F#) live in
+        // Files in WASM-only languages (Gleam, Julia, F#) live in
         // `file_hashes` because the JS-side WASM backfill writes them, but
         // Rust's narrower file_collector never collects them. Without this
         // skip, every incremental rebuild would flag them as removed and
         // purge their rows — the #1066 ~2s floor.
         let mut existing = HashMap::new();
         for path in [
-            "tests/fixtures/clojure/main.clj",
             "tests/fixtures/gleam/main.gleam",
             "tests/fixtures/julia/main.jl",
             "tests/fixtures/fsharp/Main.fs",