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

docs/explanation/pipeline-rationale.md

@@ -0,0 +1,78 @@
+# Why the pipeline has four stages
+
+Chemenu could, in principle, be one directory: drop a file in, ask a question, get an answer
+computed fresh each time. It isn't built that way. The pipeline in
+[AGENTS.md](../../AGENTS.md#routing) - `raw/` -> `[types/ + tools/]` -> `kb/` -> `reports/`, with
+`work/` alongside rather than inside it - separates *material* from *meaning* from
+*byproduct*, and each seam exists because collapsing it costs something specific.
+
+## Why raw material stays untouched
+
+[raw/CONTRACT.md](../../raw/CONTRACT.md) keeps a source exactly as it arrived. The reasoning is
+simple once stated: the moment someone "cleans up" or reformats a source on the way in, the
+thing later claims get checked against is no longer the thing that was actually said. An
+immutable `raw/` means a citation always resolves to the original, not to somebody's tidied
+memory of it. It also draws a trust boundary in one place instead of scattering it - everything
+past `raw/` can be treated as reviewed, because nothing upstream of it silently already was.
+`incoming/` sits entirely on the near side of that boundary: a file waiting there is
+not yet reviewed and not yet a citation target, so its being gitignored and readable by an
+ingest session does not weaken anything - the boundary is the promotion into `raw/` itself, not
+the moment a human happened to drop a file somewhere.
+
+Once a document can arrive from *outside* - the MCP server's optional `submit` tool - "a human
+happened to drop a file somewhere" stops describing how everything reaches `incoming/`, so the
+near side of the boundary gets a stage of its own rather than a second meaning. `mcp-upload/`
+holds what nobody has looked at yet; `incoming/` holds what someone has. Two arrows, two
+different things being granted: `upload accept` grants *trust* (a human read the material and
+took responsibility for it), `raw accept` grants *immutability* (it becomes a citation target
+and stops being editable). Collapsing them would have meant one of the two lying - either an
+unreviewed stranger's file sitting in the same directory a human's own drop does, or the
+promotion into `raw/` quietly doubling as the review step it cannot perform.
+
+## Why extraction happens once, through a schema
+
+[types/type-spec.md](../../types/type-spec.md) is what stands between a raw file and a `kb/` page:
+a type-spec defines what a conforming instance of a page looks like, and the compiler
+(`tools/wikitool`) applies it. The alternative - every query re-reading and re-interpreting the
+source on demand - would mean paying the cost of understanding the material every single time,
+and getting a slightly different answer each time depending on how the question was phrased.
+Extracting once, against a fixed schema, turns "re-read and re-guess" into "look up what was
+already compiled." That is the "never re-derive, always compile" principle from
+[AGENTS.md](../../AGENTS.md): understanding a source is expensive and worth doing exactly once,
+after which it becomes a cheap, stable lookup.
+
+## Why a `kb/` page has to stand on its own
+
+[kb/CONTRACT.md](../../kb/CONTRACT.md) sets the bar for the compiled layer: a page should answer a
+future question without sending the reader back to the source it came from. That's the payoff
+of compiling in the first place - if every answer still bottomed out in "go re-read the raw
+file," the `kb/` layer would just be a pointer with extra steps, and the cost of extraction
+would have bought nothing. A page that stands alone is what makes the corpus fast and
+consistent to query: the work of understanding is already sitting there, done.
+
+## Why `reports/` doesn't need to be maintained
+
+[reports/CONTRACT.md](../../reports/CONTRACT.md) treats most of what lands in `reports/` -
+lint output, telemetry traces - as disposable. The structural content of a lint report can be
+recomputed from the tree at any commit, so keeping an old copy around would just be a second
+version of something the tool can already answer on demand, and a second copy is exactly the
+kind of thing that quietly goes stale. Treating it as derived output rather than a fourth thing
+to maintain means there is nothing there to fall out of sync - regenerating it is cheaper than
+reconciling it. The one part that genuinely can't be recomputed - the judgment a pass produced -
+is carried out into `kb/` or `kb/log.md` before the report itself is discarded, which is the
+distinction between what's recomputable and what isn't.
+
+## Where `work/` fits
+
+[work/CONTRACT.md](../../work/CONTRACT.md) describes a workshop, not a fifth pipeline stage: a
+place for the notes, extracts and open decisions of a task that spans more than one session, on
+its way toward becoming a `kb/` page. It sits beside the raw -> kb -> reports flow rather than
+inside it - closer in spirit to a desk than to a conveyor belt.
+
+## The shape this produces
+
+Four stages, each answering a different question: `raw/` - what was actually said; `types/` +
+`tools/` - how to turn that into structured understanding; `kb/` - what is now known;
+`reports/` - what a pass over the corpus noticed in passing. Keeping them separate is what lets
+each one be trusted for what it is, instead of every layer having to double as all four at
+once.