fix: ignore Rust target/ build directory during file collection (#2374)

[carlos-alm]

Summary

Neither IGNORE_DIRS (TypeScript, src/shared/constants.ts) nor its mirror DEFAULT_IGNORE_DIRS (Rust, crates/codegraph-core/src/domain/graph/builder/stages/collect_files.rs) skipped Cargo's target/ build output directory. For any non-trivial Rust project this directory can be enormous, and codegen tools (bindgen, prost, tonic-build, etc.) emit real, syntactically valid .rs files into OUT_DIR under target/ — codegraph's file walk was parsing these as hand-written project source, polluting the graph and adding real walk-time cost.

Added "target" to both lists, keeping the dual-engine mirroring convention intact.

Verification

• lint: pass
• tests: pass (full JS suite: 328 files / 5287 tests; full Rust suite: 1024 tests)
• Added unit coverage: shouldIgnore('target') + IGNORE_DIRS membership (TS), an end-to-end collectFiles() walk test with a target/debug/build.rs fixture (TS), and a collect_skips_target_dir test mirroring the existing collect_skips_ignored_dirs pattern (Rust)

Closes #2374

[greptile-apps]

Greptile Summary

Adds Cargo’s target/ directory to the default ignore sets for both collection engines.

• Keeps the TypeScript and Rust file collectors behaviorally aligned.
• Adds TypeScript and Rust coverage confirming generated files beneath target/ are excluded from full collection.

Confidence Score: 5/5

The PR appears safe to merge.

No blocking failure remains.

Important Files Changed

Filename	Overview
crates/codegraph-core/src/domain/graph/builder/stages/collect_files.rs	Adds target to the Rust collector’s mirrored default ignore list and verifies full collection skips that directory.
src/shared/constants.ts	Adds target to the TypeScript default ignore set, matching the Rust engine.
tests/unit/builder.test.ts	Extends the collection fixture and verifies files beneath target/ are excluded.
tests/unit/constants.test.ts	Verifies target belongs to the ignore set and is recognized by shouldIgnore.

_{Reviews (2): Last reviewed commit: "fix: ignore Rust target/ build directory..." | Re-trigger Greptile}

[greptile-apps]

Incremental collection retains target files

When an existing graph contains files under target/ and the next build uses incremental collection, the fast path reconstructs its file set without applying this new default ignore, causing generated Rust files to remain in the graph until a full rebuild invalidates them.

Knowledge Base Used:

• Rust Native Core and the Native/WASM Bridge
• Shared Utilities and Types

[carlos-alm]

Confirmed — this is real, but it's a general characteristic of the incremental fast path (tryFastCollect/try_fast_collect), not something specific to target: neither engine's fast path re-applies IGNORE_DIRS/DEFAULT_IGNORE_DIRS at all, so any file already in file_hashes from a prior build survives incremental rebuilds regardless of which ignore-dir entry would now exclude it. Fixing that means changing the fast path for every ignore-dir entry, which is out of scope for this PR. Filed as #2512 to track separately. Existing graphs self-heal via the documented --no-incremental full rebuild in the meantime.

[carlos-alm]

@greptileai