feat!: docs/ sorted into tutorials, how-to, reference, explanation plus unshipped docs/dev/; explanation pages and developer guide moved, human docs English (#187)

The seven explanation pages move to docs/explanation/ without a stub, DEVELOPMENT.md becomes docs/dev/development.md (translated to English), dist export leaves docs/dev/ out, docs verify rejects a file outside the five areas, and AGENTS.md states that the stack's human documentation is English. Required migration 9.0.0-docs-diataxis rewrites the old path in an instance's own kb/CONVENTIONS.md.

Files changed:
- .wikitool-kb.json
- AGENTS.md
- CHANGES.md
- CLAUDE.md
- DEVELOPMENT.md
- INSTALL.md
- README.md
- VERSION
- docs/dev/development.md
- docs/explanation/README.md
- docs/explanation/knowledge-and-commitment.md
- docs/explanation/language-boundaries.md
- docs/explanation/model-and-effort-selection.md
- docs/explanation/ownership-and-templates.md
- docs/explanation/pipeline-rationale.md
- docs/explanation/version-model.md
- docs/explanation/why-gates-are-code.md
- docs/how-to/README.md
- docs/knowledge-and-commitment.md
- docs/language-boundaries.md
- docs/model-and-effort-selection.md
- docs/ownership-and-templates.md
- docs/pipeline-rationale.md
- docs/reference/README.md
- docs/tutorials/README.md
- docs/version-model.md
- docs/why-gates-are-code.md
- instructions/CONTRACT.md
- instructions/dev/dev-setup.md
- instructions/dev/doc-pull-through.md
- instructions/dev/stack-close/SKILL.md
- instructions/dev/stack-mode.md
- instructions/gtd-weekly-review/SKILL.md
- instructions/ingest-queue.md
- instructions/migrations/6.0.0-type-guidance-split.md
- instructions/migrations/9.0.0-docs-diataxis.md
- instructions/upgrade-instance.md
- kb/CONVENTIONS.md
- kb/CONVENTIONS.md.template
- tools/CONTRACT.md
- tools/chemenu/commands/dist_cmd.py
- tools/chemenu/commands/docs_verify.py
- tools/chemenu/commands/new_page.py
- tools/chemenu/commands/task_cmd.py
- tools/chemenu/tasks/protocol.py
- tools/chemenu/tests/test_dist_cmd.py
- tools/chemenu/tests/test_docs_verify.py
- tools/chemenu/tests/test_git_publish.py
- tools/chemenu/tests/test_toc.py
- types/type-guidance.md

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

CLAUDE.md

@@ -15,4 +15,4 @@ Model and effort selection is the one remaining Claude-Code-only decision
 ([instructions/CONTRACT.md](instructions/CONTRACT.md#two-forms-three-reference-tiers) has the
 import-vs-link rule in general), and it earns a link rather than an import: a session stops to
 make this call - spawning a subagent, opening a review - rather than needing it pre-loaded before
-it has done anything. See [docs/model-and-effort-selection.md](docs/model-and-effort-selection.md).
+it has done anything. See [docs/explanation/model-and-effort-selection.md](docs/explanation/model-and-effort-selection.md).