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>

CONTRIBUTING.md

@@ -0,0 +1,53 @@
+# Contributing to ultraplan-local
+
+This is a solo project. Issues are welcome. PRs may be considered but are not expected.
+
+## Reporting bugs
+
+Open an issue with:
+- Plugin version (from `.claude-plugin/plugin.json`)
+- Claude Code version (`claude --version`)
+- What you did, what you expected, what happened instead
+- Whether it fails consistently or occasionally
+
+## Suggesting features or improvements
+
+Open an issue describing:
+- The problem you ran into
+- What you think would solve it
+- Any alternatives you considered
+
+## Design principles
+
+Changes to this plugin must preserve:
+- **Pure markdown** — no scripts, no dependencies, no platform-specific code
+- **Cross-platform** — must work identically on Mac, Linux, and Windows
+- **Cost-aware** — Sonnet for exploration, Opus only for planning
+- **Privacy-first** — never read files outside the repo, never log secrets
+- **Honest** — if a task is trivial, say so instead of inflating the plan
+
+## Architecture
+
+| File | Purpose |
+|------|---------|
+| `.claude-plugin/plugin.json` | Plugin manifest |
+| `commands/ultraplan-local.md` | The `/ultraplan-local` slash command — workflow orchestration |
+| `agents/*.md` | Specialized agents for exploration, review, and orchestration |
+| `templates/plan-template.md` | Structured plan output format |
+| `templates/spec-template.md` | Spec file format |
+
+The command file is the core. All planning logic lives in markdown.
+
+## Testing locally
+
+```bash
+claude --plugin-dir /path/to/ultraplan-local
+# Then in the session:
+/ultraplan-local <describe a task>
+```
+
+Verify:
+- Exploration agents spawn in parallel
+- Plan follows the template structure
+- Plan file is written to `.claude/plans/`
+- Adversarial review runs (plan-critic + scope-guardian)