feat(speckit): integrate github/spec-kit for spec-driven development (#38)

Installs spec-kit slash commands (/speckit-specify, /speckit-plan,
/speckit-tasks, /speckit-implement, /speckit-analyze, /speckit-clarify,
/speckit-checklist, /speckit-constitution, /speckit-taskstoissues) into
Claude Code via .claude/skills/speckit-*/.

Note: specify-cli v1.0.0 init fails on Windows because spec-kit v0.5+
releases no longer attach binary zip assets to GitHub releases (confirmed
by inspecting all 30 releases via API; only v0.4.4 and earlier have
assets). Templates were sourced directly from the github/spec-kit@v0.7.3
repo tree and SKILL.md files were built per the claude integration spec
in src/specify_cli/integrations/claude/__init__.py (user-invocable:true,
disable-model-invocation:false, argument-hint injection).

Enables the "specs in git" workflow for cross-device work state:
- New feature → /speckit-specify → specs/NNN/spec.md
- Design → /speckit-plan → specs/NNN/plan.md
- Work → /speckit-tasks → specs/NNN/tasks.md (handoff artifact)
- Implement → /speckit-implement → code

Preserves existing CLAUDE.md (@AGENTS.md bridges intact) and existing
memory policies in AGENTS.md. memory/constitution.md is annotated at
the top to reference AGENTS.md for project-specific constraints.

No change to server.mjs, models.json, package.json, or any other code.

Co-authored-by: Tao Deng <dtzp555@gmail.com>
Co-authored-by: Claude Sonnet 4.6 <noreply@anthropic.com>

.specify/templates/constitution-template.md

@@ -0,0 +1,50 @@
+# [PROJECT_NAME] Constitution
+<!-- Example: Spec Constitution, TaskFlow Constitution, etc. -->
+
+## Core Principles
+
+### [PRINCIPLE_1_NAME]
+<!-- Example: I. Library-First -->
+[PRINCIPLE_1_DESCRIPTION]
+<!-- Example: Every feature starts as a standalone library; Libraries must be self-contained, independently testable, documented; Clear purpose required - no organizational-only libraries -->
+
+### [PRINCIPLE_2_NAME]
+<!-- Example: II. CLI Interface -->
+[PRINCIPLE_2_DESCRIPTION]
+<!-- Example: Every library exposes functionality via CLI; Text in/out protocol: stdin/args → stdout, errors → stderr; Support JSON + human-readable formats -->
+
+### [PRINCIPLE_3_NAME]
+<!-- Example: III. Test-First (NON-NEGOTIABLE) -->
+[PRINCIPLE_3_DESCRIPTION]
+<!-- Example: TDD mandatory: Tests written → User approved → Tests fail → Then implement; Red-Green-Refactor cycle strictly enforced -->
+
+### [PRINCIPLE_4_NAME]
+<!-- Example: IV. Integration Testing -->
+[PRINCIPLE_4_DESCRIPTION]
+<!-- Example: Focus areas requiring integration tests: New library contract tests, Contract changes, Inter-service communication, Shared schemas -->
+
+### [PRINCIPLE_5_NAME]
+<!-- Example: V. Observability, VI. Versioning & Breaking Changes, VII. Simplicity -->
+[PRINCIPLE_5_DESCRIPTION]
+<!-- Example: Text I/O ensures debuggability; Structured logging required; Or: MAJOR.MINOR.BUILD format; Or: Start simple, YAGNI principles -->
+
+## [SECTION_2_NAME]
+<!-- Example: Additional Constraints, Security Requirements, Performance Standards, etc. -->
+
+[SECTION_2_CONTENT]
+<!-- Example: Technology stack requirements, compliance standards, deployment policies, etc. -->
+
+## [SECTION_3_NAME]
+<!-- Example: Development Workflow, Review Process, Quality Gates, etc. -->
+
+[SECTION_3_CONTENT]
+<!-- Example: Code review requirements, testing gates, deployment approval process, etc. -->
+
+## Governance
+<!-- Example: Constitution supersedes all other practices; Amendments require documentation, approval, migration plan -->
+
+[GOVERNANCE_RULES]
+<!-- Example: All PRs/reviews must verify compliance; Complexity must be justified; Use [GUIDANCE_FILE] for runtime development guidance -->
+
+**Version**: [CONSTITUTION_VERSION] | **Ratified**: [RATIFICATION_DATE] | **Last Amended**: [LAST_AMENDED_DATE]
+<!-- Example: Version: 2.1.1 | Ratified: 2025-06-13 | Last Amended: 2025-07-16 -->