chore(hooks): scope pre-edit-impact to cqs's own src/ and tests/ (#1068)

The hook was matching any path containing `/src/`, which included
vendored Rust subtrees like `cuvs-fork-push/rust/cuvs/src/`. When an Edit
fired against a cuvs file, the hook tried to invoke
`python3 .claude/hooks/pre-edit-impact.py` with cwd=cuvs-fork-push,
where that path doesn't exist — silently blocking the Edit with a
'No such file' error. Hit during today's rebase of rapidsai/cuvs#2019
to resolve a merge conflict; had to work around by writing the file via
a Python script in Bash.

Tighten the path predicate: derive cqs root from the script's own
location, then accept only files under `<cqs_root>/src/` or
`<cqs_root>/tests/`. cuvs-fork-push, evals/, samples/, and any future
vendored Rust subtree all silently bail.

Verified with four smoke cases:
- cuvs path → exit 0, no `cqs impact` invocation
- cqs/src path → exit 0, runs `cqs impact` (no output for hypothetical fns)
- cqs/tests path → exit 0, runs `cqs impact`
- cqs/evals/*.rs → exit 0, no invocation (not under src/ or tests/)

Co-authored-by: jamie8johnson <jamie8johnson@users.noreply.github.com>
Co-authored-by: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

Author: jamie8johnson

.claude/hooks/pre-edit-impact.py

@@ -4,6 +4,14 @@
 Only fires when `old_string` contains a `fn foo` / `pub fn foo` declaration.
 Non-fn edits (schema, comments, match arms, string literals) produce no output,
 keeping context injection focused on risky function-targeted changes.
+
+Scope: ONLY fires for cqs's own `src/` and `tests/` trees. Vendored Rust
+subtrees (`cuvs-fork-push/rust/`, future bundled deps) are deliberately
+skipped — `cqs impact` runs against cqs's index, which doesn't contain
+foreign Cargo workspaces, so the lookup would be empty/wrong. Earlier
+versions of this script matched any path containing `/src/`, which fired
+on cuvs-fork-push edits and blocked them with a missing-file error
+during conflict resolution.
 """
 import json
 import os
@@ -15,8 +23,19 @@
 file_path = inp.get("tool_input", {}).get("file_path", "")
 old_string = inp.get("tool_input", {}).get("old_string", "")
 
-# Only analyse Rust source files in src/
-if not file_path.endswith(".rs") or "/src/" not in file_path:
+if not file_path.endswith(".rs"):
+    sys.exit(0)
+
+# Derive cqs project root from the script's own location:
+# <cqs_root>/.claude/hooks/pre-edit-impact.py → ../../ = <cqs_root>
+CQS_ROOT = os.path.realpath(os.path.join(os.path.dirname(__file__), "..", ".."))
+
+abs_path = os.path.realpath(file_path)
+allowed_roots = (
+    os.path.join(CQS_ROOT, "src") + os.sep,
+    os.path.join(CQS_ROOT, "tests") + os.sep,
+)
+if not abs_path.startswith(allowed_roots):
     sys.exit(0)
 
 # Look for a fn / pub fn / pub async fn / pub(crate) fn declaration in old_string.