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>

plugins/ultraplan-local/skills/cc-architect-catalog/subagents-reference.md

@@ -0,0 +1,98 @@
+---
+name: subagents-reference
+description: CC subagents — how the Task tool spawns isolated agent instances with scoped tools and context.
+layer: reference
+cc_feature: subagents
+source: https://docs.claude.com/en/docs/claude-code/sub-agents
+concept: task-tool-delegation
+last_verified: 2026-04-18
+ngram_overlap_score: null
+review_status: approved
+---
+
+# Subagents — Reference
+
+Subagents are fresh Claude instances spawned via the Task tool. Each
+receives a task prompt, a tool subset, and no memory of the parent
+conversation except what the parent explicitly passes. They return a
+single final message to the parent.
+
+## Anatomy
+
+A subagent has:
+
+- **A name** — either a built-in type (`general-purpose`, `Explore`,
+  `Plan`) or a plugin-defined type (`code-reviewer`, `test-runner`,
+  ...).
+- **A system prompt** — defined by the agent type. The parent cannot
+  override it.
+- **A tool set** — subset of the parent's tools, as declared in the
+  agent definition's frontmatter `tools:` field.
+- **A task prompt** — what the parent asks it to do. Self-contained;
+  the subagent has no access to prior messages.
+- **A model** — either explicit in the agent definition (`model: opus |
+  sonnet | haiku`) or inherited from the parent.
+
+## How to define a subagent
+
+A plugin agent is a markdown file in `agents/` with frontmatter:
+
+```yaml
+---
+name: code-reviewer
+description: <when to invoke, include examples>
+model: sonnet
+tools: ["Read", "Grep", "Glob"]
+---
+
+<system prompt content>
+```
+
+The `description` field is how Claude decides when to spawn this
+subagent. Include concrete trigger examples.
+
+## How to invoke
+
+Parent calls the `Task` / `Agent` tool with:
+
+- `subagent_type` — the agent's name
+- `description` — short label for logs
+- `prompt` — the self-contained task
+
+Optional:
+
+- `run_in_background: true` — agent runs in the background; parent
+  is notified on completion.
+- `isolation: "worktree"` — agent runs in a temporary git worktree
+  (isolated copy of the repo).
+
+## Return protocol
+
+- Foreground agent: parent blocks until the agent returns. Return value
+  is a single text message.
+- Background agent: parent continues. On completion, the harness
+  injects a notification into the parent's next turn.
+
+## Isolation guarantees
+
+- No conversation history sharing. Each subagent starts cold.
+- Separate context window. A subagent can read large files without
+  polluting the parent's context.
+- Separate tool permissions. A subagent with only `Read` tools cannot
+  write files, even if the parent can.
+
+## Cost and latency
+
+- Every subagent call is a full model call with its own token budget.
+- Model choice matters: Sonnet is ~5× cheaper than Opus; Haiku is
+  cheaper still but cannot be used (per project policy).
+- Parallel subagents: the parent can launch multiple in one message;
+  the harness runs them concurrently. Total latency ≈ slowest agent.
+
+## Failure modes
+
+- Subagent hits context limit → partial or missing return.
+- Subagent runs in background and the parent conversation ends → result
+  may be orphaned.
+- Subagent's return message hallucinates file paths → caller must
+  verify.