feat(ultraplan-local): v1.6.0 — /ultraresearch-local deep research command

Add /ultraresearch-local for structured research combining local codebase
analysis with external knowledge via parallel agent swarms. Produces research
briefs with triangulation, confidence ratings, and source quality assessment.

New command: /ultraresearch-local with modes --quick, --local, --external, --fg.
New agents: research-orchestrator (opus), docs-researcher, community-researcher,
security-researcher, contrarian-researcher, gemini-bridge (all sonnet).
New template: research-brief-template.md.

Integration: --research flag in /ultraplan-local accepts pre-built research
briefs (up to 3), enriches the interview and exploration phases. Planning
orchestrator cross-references brief findings during synthesis.

Design principle: Context Engineering — right information to right agent at
right time. Research briefs are structured artifacts in the pipeline:
ultraresearch → brief → ultraplan --research → plan → ultraexecute.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

templates/session-spec-template.md

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+# Session {N}: {title}
+
+> From master plan: {plan file path}
+> Session {N} of {total sessions}
+
+## Context
+
+{Why this session exists. What it accomplishes within the larger plan.
+Include enough background that an executor with no prior context can understand
+the purpose and make judgment calls.}
+
+## Dependencies
+
+- **Depends on:** {Session M | "none — can run in parallel"}
+- **Blocks:** {Session P | "none"}
+- **Entry condition:** {what must be true before this session starts — e.g., "Session 2 committed and tests pass"}
+
+## Scope Fence
+
+- **Touch:** {explicit list of files this session may create or modify}
+- **Never touch:** {files that belong to other sessions — hard boundary}
+
+## Steps
+
+### Step 1: {description}
+
+- **Files:** `{path}`
+- **Changes:** {exactly what to modify}
+- **Reuses:** {existing function/pattern, with file path}
+- **Test first:** {test file, what it verifies, pattern to follow}
+- **Verify:** `{exact command}` → expected: `{output}`
+- **On failure:** {revert | retry | skip | escalate} — {specific instructions}
+- **Checkpoint:** `git commit -m "{message}"`
+
+### Step 2: {description}
+
+{same structure as Step 1}
+
+## Exit Condition
+
+All of these must pass before this session is considered complete:
+
+- [ ] `{verification command}` → expected: `{output}`
+- [ ] `{verification command}` → expected: `{output}`
+- [ ] All changes committed with descriptive messages
+- [ ] No uncommitted changes remain (`git status` clean)
+
+## Failure Handling
+
+- If ANY step fails after retry: **stop execution**. Do NOT proceed to later steps.
+- Commit whatever was completed successfully before stopping.
+- Report which step failed, the error message, and what was attempted.
+
+## Handoff State
+
+{What the next session (or final verification) needs to know about this session's
+output. Include: new files created, exports added, configuration changed, APIs
+introduced. This section bridges sessions — it's the "baton" in a relay race.}
+
+## Metadata
+
+- **Master plan:** `{plan file path}`
+- **Steps from plan:** {step N}–{step M}
+- **Estimated complexity:** {low | medium | high}
+- **Model recommendation:** {opus | sonnet} — {rationale}