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/version-parts.md

@@ -92,7 +92,8 @@ a new one, and only `version release` turns it into something the release workfl
 
 ## When to run
 
-Before every `tools/wikitool version bump` - the `stack-dev` skill's step 4 sends you here.
+When a design names the version part (`stack-dev` step 4), and again before every
+`tools/wikitool version bump` (`stack-build` step 4).
 Read it in full the first time a change looks like it might be boundary-crossing; afterwards
 the three-line test below is usually enough.