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/commonplace-kb.md

@@ -24,5 +24,6 @@ carries it (see [tools/CONTRACT.md](../../tools/CONTRACT.md) for what `dist expo
 
 ## Scope
 
-Only relevant while working in [stack-dev](stack-dev/SKILL.md) mode. Not part of the wiki
+Only relevant in a stack-development session ([stack-mode.md](stack-mode.md)), mostly while
+designing. Not part of the wiki
 content pipeline, and not linked from anything outside `instructions/dev/`.