feat: use git root for consistent project name detection

[Boltthecat19]

Problem

getProjectName() uses path.basename(cwd) to identify the current project. This produces inconsistent names when Claude is invoked from a subdirectory — e.g. working in my-project/src/utils yields a project name of utils, not my-project. Running from the home directory yields the username.

This causes observations and memory to be siloed under incorrect project names, breaking cross-session context.

Solution

Add a findGitRoot() utility (src/utils/git-root.ts) that walks up the directory tree from cwd looking for a .git entry (directory or file, to support worktrees). The git root directory name is used as the project identifier. Non-git directories fall back to the existing path.basename(cwd) behavior.

Changes

• src/utils/git-root.ts — new utility, walks cwd upward to find .git
• src/utils/project-name.ts — prefer git root name, fall back to basename
• tests/utils/git-root.test.ts — 6 unit tests: null input, no git, cwd root, subdirectory, worktree (.git file)
• tests/utils/project-name.test.ts — 5 unit tests covering all branches

Test Results

All 11 new tests pass in isolation and with --no-parallel.

Note: The full bun test suite shows 5 spurious failures for getProjectName caused by a pre-existing mock.module() leak in tests/hooks/context-reinjection-guard.test.ts:32 that pollutes parallel test workers. This is unrelated to this PR and will be addressed separately.

[xkonjin]

Quick review pass:

• Main risk area here is input validation, path handling, and malformed payload behavior.
• Good to see test coverage move with the code; I’d still make sure it exercises the unhappy path around input validation, path handling, and malformed payload behavior rather than only the happy path.
• Before merge, I’d smoke-test the behavior touched by git-root.ts, project-name.ts, git-root.test.ts (+1 more) with malformed input / retry / rollback cases, since that’s where this class of change usually breaks.