Add v0.6.0: full skill/agent QA pass, 3 new agents tested, template cleanup

Skills fixed: sprint-status (stale escalation, threshold), retrospective
(existing file detection, missing data fallback), changelog (misc category,
task-ref count), patch-notes (BLOCKED on missing changelog, tone/template
paths), story-readiness (Phase 0 mode resolution, QL-STORY-READY gate),
art-bible, brainstorm, design-system, ux-design, dev-story, story-done,
create-architecture, create-control-manifest, map-systems, propagate-design-change,
quick-design, prototype, asset-spec.

Agents fixed: all 4 directors (gate verdict token format), engine-programmer,
ui-programmer, tools-programmer, technical-artist (engine version safety),
gameplay-programmer (ADR compliance), godot-gdextension-specialist (ABI warning),
systems-designer (escalation path to creative-director), accessibility-specialist
(model, tools, WCAG criterion format, findings template), live-ops-designer
(escalation paths, battle pass value language), qa-tester (model, test case
format, evidence routing, ambiguous criteria, regression scope).

Specs updated: smoke-check and adopt specs rewritten to match actual skill
behavior. catalog.yaml reset to blank template state. Removed
session-state marketing research file, removed session-state from gitignore.

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

.claude/agents/tools-programmer.md

@@ -73,6 +73,14 @@ Before writing any code:
 5. **Documentation**: Every tool must have usage documentation and examples.
    Tools without documentation are tools nobody uses.
 
+### Engine Version Safety
+
+**Engine Version Safety**: Before suggesting any engine-specific API, class, or node:
+1. Check `docs/engine-reference/[engine]/VERSION.md` for the project's pinned engine version
+2. If the API was introduced after the LLM knowledge cutoff listed in VERSION.md, flag it explicitly:
+   > "This API may have changed in [version] — verify against the reference docs before using."
+3. Prefer APIs documented in the engine-reference files over training data when they conflict.
+
 ### Tool Design Principles
 
 - Tools must validate input and give clear, actionable error messages