feat: stack development in three phases - stack-dev (design), stack-build, stack-close, handed over through tracker states (#168)

stack-build and stack-close carry disable-model-invocation, so each phase change is
the operator's slash command; no skill offers a mid-session /model or /effort switch.
Mode rules and the phase table move to instructions/dev/stack-mode.md, publish and CI
waiting to instructions/dev/publish-and-ci.md, the ready definition to issue-tracking.md.

Files changed:
- AGENTS.md
- CHANGES.md
- DEVELOPMENT.md
- README.md
- VERSION
- docs/model-and-effort-selection.md
- instructions/CONTRACT.md
- instructions/dev/commonplace-kb.md
- instructions/dev/dev-setup.md
- instructions/dev/doc-pull-through.md
- instructions/dev/issue-tracking.md
- instructions/dev/publish-and-ci.md
- instructions/dev/stack-build/SKILL.md
- instructions/dev/stack-close/SKILL.md
- instructions/dev/stack-dev/SKILL.md
- instructions/dev/stack-mode.md
- instructions/dev/testing-conventions.md
- instructions/dev/version-parts.md
- tools/chemenu/commands/git_publish.py
- tools/chemenu/tests/test_git_publish.py
- tools/chemenu/tests/test_instructions_cmd.py

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01SnAJ7Z3CpVD3PRbN73QtU2

instructions/dev/dev-setup.md

@@ -25,8 +25,8 @@ development material under `instructions/dev/` and `commonplace/`, and no
    instance.
 
 2. **Run [bootstrap.md](../bootstrap.md)** - the preflight, then `tools/wikitool instructions
-   sync`. That publishes `stack-dev` and `stack-close` along with the content skills; both exist
-   only in this repository.
+   sync`. That publishes `stack-dev`, `stack-build` and `stack-close` along with the content skills;
+   all three exist only in this repository.
 
 3. **Record the environment** (bootstrap.md step 5). Here it is worth the minute: which harness,
    that `gitea-mcp` reaches the tracker and CI, which remote `publish` talks to. Every stack-dev