CI: add code-size check for files crossing LOC threshold (#12810)

* CI: add code-size check for files crossing LOC threshold

* feat(ci): add duplicate function detection to CI code-size check

The --compare-to mode now also detects new duplicate function names
introduced by a PR. Uses git diff to scope checks to changed files
only, keeping CI fast.

* fix(ci): address review feedback for code-size check

- Validate git ref upfront; exit 2 if ref doesn't exist
- Distinguish 'file missing at ref' from genuine git errors
- Explicitly fetch base branch ref in CI workflow
- Raise threshold from 700 to 1000 lines

* fix(ci): exclude Swabble, skills, .pi from code analysis

* update gitignore for pycache

* ci: make code-size check informational (no failure on violations)

.gitignore

@@ -7,6 +7,8 @@ pnpm-lock.yaml
 bun.lock
 bun.lockb
 coverage
+__pycache__/
+*.pyc
 .tsbuildinfo
 .pnpm-store
 .worktrees/