feat(mcp): expose thread workspace inventory

[juliusmarminge]

An agent can otherwise see only the branch and worktree path recorded on its thread, which does not establish whether Git agrees, which physical checkouts exist, or which live threads own them.

This change enriches t3_worktree_status with separate recorded and actual state, and adds bounded t3_worktree_list discovery. A dedicated Git inventory path reports canonical repository common-directory and physical worktree-root identities, including detached and stale registrations, without changing the existing paginated vcs.listRefs wire/cache shape.

Results are current-project scoped and read-only. Pages are sliced before status I/O; nested and symlinked recorded paths are resolved through actual Git identity; independent nested repositories are not misattributed; ordinary typed inventory failures make binding counts explicitly incomplete while interruption and defects propagate.

Focused validation:

• 241 lower-layer tests across real Git inventory, MCP status/list, registration, Claude exposure, contracts, client-runtime cache compatibility, and presentation
• vp run --filter t3 typecheck
• vp run --filter @t3tools/contracts typecheck
• vp run --filter @t3tools/shared typecheck
• vp run --filter @t3tools/client-runtime typecheck
• Targeted vp lint, vp fmt --check, and git diff --check

Review base: t3code/codex-turn-mapping at 415ed0f73b97f1655b6282492f81d0b2bba3a9cc. Native stack: #8685 → #8680. This discovery layer does not add lifecycle pruning, revival, or cleanup.

Implemented by GPT-5.6-Sol via Codex in T3 Code.

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[github-actions]

Thread transfer impact

⚠️ The latest CI run did not produce a thread transfer result for 718558b.

This comment will update automatically after the next completed run.

[macroscopeapp]

Approvability

Verdict: Not approved

Macroscope's review found this PR not approvable — This PR adds a model-visible worktree inventory capability and substantially expands existing worktree status behavior across MCP, contracts, orchestration, and Git infrastructure. The cross-layer runtime impact and non-trivial inventory/path-resolution logic warrant human review.

No code changes detected at 718558b. Prior analysis still applies.

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[macroscopeapp]

Macroscope has since reviewed this pull request. An earlier review was skipped by a cost limit; a review has now completed, so that notice no longer applies.

[cursor]

Cursor Bugbot has reviewed your changes using high effort and found 1 potential issue.

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[juliusmarminge]

Superseded as the active MCP proposal by #10566 in the rebuilt MCP stack, following the maintainer request to review thin service wrappers separately from service hardening.

This is not a full feature-parity replacement. This discovers branch-backed refs/worktrees only. Detached unbound inventory and switching an existing checkout require a shared service operation and are intentionally not rebuilt inside MCP. The old workspace work is retained for that extraction.

Closing this mixed proposal without merging. The remote branch agents/mcp-workspaces/inventory and exact head 718558bfe90355b4e072ef0279d4115d6f8e10fc are retained so the service changes can be extracted for separate review later.