Git worktrees resolve to main worktree's memory directory instead of their own

Description

When Claude Code is launched from a manually created git worktree, the auto memory directory resolves to the main worktree's project path instead of the linked worktree's path.

Reproduction

# Setup: Monocle-a is the main worktree, Monocle-b is a linked worktree
git worktree list
# /Users/george/Code/Monocle-a  742e462 [main]         ← main worktree
# /Users/george/Code/Monocle-b  742e462 [Monocle-b]    ← linked worktree

Launch Claude Code from the linked worktree:

cd /Users/george/Code/Monocle-b
claude

Expected: Memory directory = ~/.claude/projects/-Users-george-Code-Monocle-b/memory/
Actual: Memory directory = ~/.claude/projects/-Users-george-Code-Monocle-a/memory/

The system prompt contains:

You have a persistent auto memory directory at \/Users/george/.claude/projects/-Users-george-Code-Monocle-a/memory/\

Even though CWD is /Users/george/Code/Monocle-b and git rev-parse --show-toplevel returns /Users/george/Code/Monocle-b.

Root cause

Claude Code appears to use git rev-parse --git-common-dir (or equivalent) to derive the project path, which returns the main worktree's .git directory for all linked worktrees:

cd /Users/george/Code/Monocle-b
git rev-parse --git-common-dir
# /Users/george/Code/Monocle-a/.git

This causes both worktrees to map to the same project directory (-Users-george-Code-Monocle-a), even though ~/.claude/projects/-Users-george-Code-Monocle-b/memory/MEMORY.md exists with correct Monocle-b-specific content that never gets loaded.

Impact

• Memory written for the linked worktree goes to the wrong project directory (the main worktree's)
• The correct memory file at -Users-george-Code-Monocle-b/memory/ is never loaded
• Two independent stacks (different branches, different deployments, different VIPs) share a single memory file, causing cross-contamination
• This is distinct from #24382 which discusses CWD-based path derivation — this bug is specifically about git common dir resolution overriding the CWD path

Environment

• Claude Code: 2.1.77 (@anthropic-ai/claude-code)
• macOS Darwin 25.4.0 (arm64)
• Git worktree created manually via git worktree add

Related

• #24382 (closed as completed, but the underlying worktree resolution issue persists for manually created worktrees)
• #16600, #15776