fix(git): resolve canonical_root '..' components for worktree git_common_dir

[lg320531124]

What Problem This Solves

When a project is inside a git worktree and git_common_dir is a relative path (e.g. ../.git), derive_canonical_root joins it with worktree_root producing /workspace/../.git. After stripping the /.git suffix, the result is /workspace/.. which realpath-resolves to the parent directory, not the workspace root.

This caused detect_changes to return empty impacted_symbols because the canonical root path prefix mismatch meant git diff paths could not be matched to graph file paths.

Example from #659:

• Actual git root: /Users/openclaw/.openclaw/workspace/
• computed canonical_root: /Users/openclaw/ (one .. too many)
• git diff path: scripts/solar_daily_report_v1.py
• Expected matching path: solar_daily_report_v1.py (relative to root_path)

Why This Change Was Made

Added realpath() call after stripping /.git to resolve any remaining .. path components. This normalizes /workspace/.. → /parent_of_workspace correctly, matching the actual git repository root.

Falls back to the un-resolved path if realpath() fails (e.g. path doesn't exist during testing).

Evidence

• Built and tested on macOS arm64 with a linked git worktree
• Before fix: canonical_root = /Users/lg/project/ (parent dir)
• After fix: canonical_root = /Users/lg/project/codebase-memory-mcp (correct git root)
• detect_changes now returns correct impacted_symbols for worktree projects
• Regular (non-worktree) repos unaffected

Fixes #690, fixes #659

[DeusData]

Huge thanks for opening this PR and for the work you put into it.

The maintainer shop is currently full, so this may sit for a bit before it gets a proper review. We will come back to this as soon as possible with real feedback; I wanted to make sure it did not sit unacknowledged in the meantime.

[DeusData]

Thanks, this looks focused. Before merge, please rewrite the commit metadata to remove generated/co-author/session attribution. DCO otherwise appears to be present on the non-merge commit.

[lg320531124]

Done — rewrote the commit metadata to drop the Co-Authored-By trailer (head now cc8344a). The Signed-off-by DCO line and the rest of the message are unchanged. Ready for merge.

[DeusData]

Thanks, confirmed the metadata cleanup. Current checks and DCO are green; this is back in the maintainer review queue.