feat(ultraplan-local): v2.2.0 — /ultra-cc-architect-local

New optional command between /ultraresearch-local and /ultraplan-local that
matches brief+research against Claude Code features (hooks, subagents, skills,
output-styles, MCP, plan-mode, worktrees, background-agents) and produces an
architecture note with brief-anchored rationale plus explicit gaps.

Added:
- commands/ultra-cc-architect-local.md (--project, --fg, --quick, --no-gaps)
- agents/architect-orchestrator.md (opus) — 6-phase background orchestrator
- agents/feature-matcher.md (sonnet) — fallback-ranked feature proposals
- agents/gap-identifier.md (sonnet) — 4 gap classes with issue-ready drafts
- agents/architecture-critic.md (sonnet) — hallucination gate as BLOCKER
- skills/cc-architect-catalog/ — SKILL.md + 10 seed entries (reference/pattern)

Changed (non-breaking):
- commands/ultraplan-local.md — auto-discovers architecture/overview.md
- agents/planning-orchestrator.md — cross-references cc_features_proposed
- plugin.json — 2.1.0 → 2.2.0, description, cc-architecture keyword
- CHANGELOG, README, CLAUDE.md (plugin + marketplace root)

Pipeline becomes brief → research → architect → plan → execute. Architect is
optional; existing project dirs keep working unchanged.

Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>

skills/cc-architect-catalog/worktrees-reference.md

@@ -0,0 +1,68 @@
+---
+name: worktrees-reference
+description: CC git worktree integration — isolated repo copies per agent for parallel or destructive work.
+layer: reference
+cc_feature: worktrees
+source: https://docs.claude.com/en/docs/claude-code/worktrees
+concept: git-worktree-isolation
+last_verified: 2026-04-18
+ngram_overlap_score: null
+review_status: approved
+---
+
+# Worktrees — Reference
+
+Git worktrees let a repo check out multiple branches simultaneously in
+separate directories. Claude Code integrates with worktrees to give
+agents isolated filesystem scopes — one agent's edits cannot clash
+with another's.
+
+## How it surfaces in CC
+
+- **`isolation: "worktree"` on a subagent call** — the harness creates
+  a temporary worktree for the subagent. The subagent runs with its
+  cwd set to the worktree. Changes stay there until merged or
+  discarded.
+- **`/worktree` skill / command** — interactive tooling for creating,
+  listing, and merging worktrees during a session.
+- **Auto-cleanup** — worktrees created by subagents are removed if the
+  subagent made no changes. Otherwise the path is returned in the
+  result for the caller to review.
+
+## Branch semantics
+
+- Each worktree checks out a named branch. Two worktrees cannot check
+  out the same branch (git's rule).
+- Creating a worktree creates a branch if one does not exist.
+- Deleting a worktree does not delete the branch; use `git branch -d`
+  separately if desired.
+
+## Use cases
+
+- **Parallel exploration** — three subagents trying three approaches,
+  each in its own worktree. The parent compares diffs.
+- **Destructive experiments** — upgrade a dependency, run the full
+  test suite, measure breakage. Discard the worktree if results are
+  bad.
+- **Long-running session without blocking main** — execute a refactor
+  in a worktree while continuing other work in the main checkout.
+
+## Pitfalls
+
+- **Shared state leaks** — node_modules, .env, build artifacts are
+  per-worktree but may be symlinked in ways that defeat isolation.
+  Verify.
+- **Disk use** — each worktree is a full checkout of the tree. For
+  large repos, disk pressure adds up.
+- **Branch proliferation** — agents that create worktrees without
+  cleanup leave orphan branches. Prune periodically.
+- **Not a sandbox** — a worktree isolates files, not network or
+  processes. A subagent in a worktree can still call the outside
+  world.
+
+## Composition
+
+- Worktrees + background agents: a background agent in a worktree can
+  work on a long task while the user continues in the main checkout.
+- Worktrees + subagents + hooks: hooks fire inside the worktree cwd,
+  so path-based hooks naturally scope to the isolated work.