feat(sdd-export): bridge engram artifacts to team-readable local files

[angel-r]

Summary

• Adds a new /sdd-export [change] skill that reads SDD artifacts (proposal, specs, design) from engram and writes them as local files following the openspec directory convention
• Enables non-developer team members (product, QA, designers) to review specs in their IDE or on GitHub without needing access to engram
• One-way, on-demand snapshot — engram remains the source of truth

Why this matters

Today, teams using SDD with engram mode get excellent developer experience (persistent memory, context recovery, no file clutter), but specs live in a black box invisible to the rest of the team. This creates a gap:

Role	Needs	Current access
Product	Review proposals & specs before implementation	None (engram only)
QA	Read scenarios to plan testing, suggest edge cases	None (engram only)
Designers	Validate UX requirements in specs	None (engram only)

/sdd-export bridges this gap without sacrificing any engram benefits.

How it works

Developer runs: /sdd-export my-feature

engram (source of truth)          →    local files (team-readable)
  sdd/my-feature/proposal         →    openspec/changes/my-feature/proposal.md
  sdd/my-feature/spec             →    openspec/changes/my-feature/specs/{domain}/spec.md
  sdd/my-feature/design           →    openspec/changes/my-feature/design.md
  sdd/my-feature/explore          →    openspec/changes/my-feature/exploration.md

Key behaviors:

• Cross-mode: always reads engram, always writes filesystem (independent of artifact_store.mode)
• On-demand: developer controls when to publish specs for review
• Idempotent: re-export overwrites with latest engram state
• Branch-aware: files travel with git branches (main = prod specs, feature/x = in-progress specs)
• Not a DAG phase: utility command, does not affect the SDD lifecycle

Team workflow enabled

1. Developer runs SDD phases as usual (propose → spec → design → tasks → apply)
2. When specs are ready for review: /sdd-export my-feature
3. Push branch — team sees specs on GitHub
4. Team reviews and creates issues for: missing edge cases, new validations, behavior changes
5. Developer updates specs, re-exports

Files changed

• skills/sdd-export/SKILL.md — new skill definition (157 lines)

Test plan

• Dog-fooded: exported this change's own artifacts successfully
• Verify skill installs correctly via the installer (glob sdd-* picks up sdd-export)
• Test with a change that has all 4 exportable artifacts (explore, proposal, spec, design)
• Test with missing optional artifacts (graceful skip — only proposal exported, others skipped with suggestions)
• Test re-export overwrites correctly (updated engram content reflected in overwritten file)

🤖 Generated with Claude Code