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

README.md

@@ -450,9 +450,9 @@ tools/wikitool <command> -h
 
 <!-- dist:strip-start -->
 Dev-instance-only: extending `tools/wikitool`, the type schema, or the instruction/skill layer
-itself is a separate session type with its own rules, covered by the `stack-dev` skill nested
-under `instructions/dev/` (never present in a distributed instance - `tools/CONTRACT.md`
-explains why).
+itself is a separate session type with its own rules, covered by the `stack-dev`,
+`stack-build` and `stack-close` skills nested under `instructions/dev/` (never present in a
+distributed instance - `tools/CONTRACT.md` explains why).
 <!-- dist:strip-end -->
 
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