feat(P03): multi-project support, NFR milestone versioning, phase context reset, install scripts

---ci---
phase: 3
milestone: v0.3.0
status: complete
decisions:
  - id: D-006
    decision: Multi-project via .ci/<slug>/ subdirectories and config.json registry
    rationale: Backward compatible migration from flat files; slug-based namespacing for branches and commits
    confidence: 0.92
    alternatives: [Git worktrees, Separate repos with subtrees]
  - id: D-007
    decision: NFR milestones use progressive patch versioning (no minor tag)
    rationale: NFR phases (fix/chore/docs/perf/refactor/test) don't represent feature delivery; patch increments reflect incremental improvement only
    confidence: 0.90
    alternatives: [Treat all milestones uniformly, Skip versioning for NFR]
  - id: D-008
    decision: Phase context reset via git checkpoint + fresh agent spawn
    rationale: Git-native architecture makes full state serialization safe; fresh context prevents accumulated conversation drift
    confidence: 0.88
    alternatives: [Context compaction, Sliding window summarization]
  - id: D-009
    decision: Install via both npm postinstall and standalone bash script
    rationale: Postinstall only fires on npm install -g; standalone script covers manual/cloned installs
    confidence: 0.95
    alternatives: [Postinstall only, Makefile target]
---/ci---

Source code:
- Added ProjectEntry, projects[], active_project to CIConfig
- Added project?: string to CiMetadata, CommitScope, all commit input types
- CiFiles: multi-project support (projectSlug, listProjects, addProject, migrateFlatToProject, isNfrMilestone)
- GitContext: projectSlug support, detectProjectFromCommit(), isNfrMilestone()
- GitBranch: project-prefixed branch naming via prefix()
- commit-builder/parser: project field in ---ci--- blocks
- config.ts: initCI() accepts projectSlug/projectName
- Implemented parseRoadmapMd phase parsing
- 284 tests passing (66 new tests)

Install scripts:
- scripts/install.sh: Standalone bash installer
- scripts/postinstall.js: npm postinstall (global installs only)

OpenCode integration:
- All 18 agents updated with multi-project project_context
- All 11 workflows updated with Step 0: Confirm Active Project
- All 5 references updated (branch-strategy, ci-files-discipline, commit-schema, decision-engine, git-context-loading)
- All 3 contexts updated (dev, research, review)
- VERSION bumped to 0.3.0

Package:
- Added files field, postinstall script, install script alias
- Version bumped to 0.3.0

opencode/agents/ci-doc-writer.md

@@ -20,6 +20,13 @@ If the prompt contains a `<files_to_read>` block, you MUST use the Read tool to
 </role>
 
 <project_context>
+If .ci/config.json has projects[] with length > 0, you are in multi-project mode.
+- Read active_project from .ci/config.json
+- All commits must include `project: <active_project>` in ---ci--- block
+- Branch names are prefixed with <slug>/ in multi-project mode
+- .ci/ files are in .ci/<slug>/ subdirectories
+If single-project mode (projects[] empty or absent), use existing conventions.
+
 Before writing, load context from git first:
 
 1. Run `git log --max-count=20` for recent changes that affect docs