docs: trim CONTEXT.md to a glossary and demote VISION.md

Why: CONTEXT.md is an instructed every-session read at 33,799 bytes (~8,450
tokens), and CONTEXT.md:17 layered docs/VISION.md on top. After the AGENTS.md
trim, that left ~9,650 tokens of instructed reads sitting behind a file whose
own format contract — grill-with-docs/CONTEXT-FORMAT.md:43, "Keep definitions
tight. One sentence max." — it was not following. 22 glossary entries averaged
190 words; the top four were 55% of the file, and one ("Vale audit prefilter")
was 1,444 words of pre-commit forensics filed as a definition.

Implementation notes:
- CONTEXT.md rewritten to CONTEXT-FORMAT.md's prescribed template: ## Language
  (five clusters, 22 terms with _Avoid_ aliases), ## Relationships,
  ## Example dialogue, ## Flagged ambiguities. 33,799 -> 9,762 bytes.
- Vale prefilter forensics moved to docs/spec/gates.md under nine subsections:
  the two-copy style layout, vale-wrap.sh and the Vale 3.15.2
  text.frontmatter.description limitation, the --config argv defect (E100),
  glob scoping, the rule inventory, and 0-files-means-NOT-RUN.
- Instruction-file format and the bidirectional-reference principle moved to
  docs/spec/architecture.md, the latter flagged as aspirational: no instruction
  file carries a `when:` field, only 2 of 39 skills do, and the reference
  scanner script it names does not exist.
- Added a per-plugin scope table to architecture.md so "which plugin owns this
  skill" survives the trim, and corrected its claim that the content index
  lives in providers/claude-code/CLAUDE.md — that file is now two import lines
  and the index sits in core/AGENTS.md.
- "Repo and Gitea are the only source of truth" moved from CONTEXT.md's
  Principles into AGENTS.md session rules; it was operative guidance in a
  glossary. docs/VISION.md and LESSONS.md added to the on-demand list.
- The apm-consumed install entry (432 words) was deleted outright: all four
  consequences are already carried by README.md, ADR-0018, gates.md and
  AGENTS.md.
- ADR-0013, ADR-0015 and ADR-0017 each pointed at CONTEXT.md sections that
  moved; amended with dated supersession notes rather than left dangling.

Impact: the every-session set drops from ~15,700 to ~4,140 tokens across both
passes (-74%). The deleted "lint plugin" entry was also stale on a safety
claim — it said lint-runner inherits Edit, but ADR-0016 restored
`disallowedTools: Edit, Write, NotebookEdit` and CONTEXT.md was never updated.

Refs: #99

docs/adr/0013-vale-harness-scope-and-rule-sources.md

@@ -9,6 +9,12 @@ deferred PR #85 review item to broaden that coverage, retroactively captures #84
 (since it was never recorded as a decision in its own right), and layers the expansion on top
 without reversing or weakening the original four rules.
 
+**2026-08-17 amendment.** The CONTEXT.md section named above no longer holds that documentation.
+CONTEXT.md was cut back to a glossary and the prefilter's mechanics — the two-copy style layout,
+`vale-wrap.sh`, the `--config` argv defect, the rule inventory, and the 0-files-means-NOT-RUN
+fallback — moved to `docs/spec/gates.md`. Read that file, not CONTEXT.md, for the harness itself;
+this ADR still owns the scope decision.
+
 **File scope stays the same.** `SKILL.md` plus agent files (`**/agents/*.md`,
 `**/*.agent.md`) only — matching the existing prefilter's globs. Skill-level
 `README.md` files and `plugin.json` manifests are not added: README.md files are navigational, not

docs/adr/0015-apm-replaces-plugin-marketplace-authoring.md

@@ -56,6 +56,8 @@ new hand-maintained manifest format.
   that work through to merge.
 - `CONTEXT.md`'s "Plugin"/"Plugin marketplace" glossary entries were rewritten in issue #90 to
   describe the compiled-output model directly, rather than carrying a forward-pointer to this ADR.
+  Superseded 2026-08-17: CONTEXT.md was cut back to one-line definitions, and the compiled-output
+  model is now described in `docs/spec/architecture.md`.
 
 ## Considered options
 

docs/adr/0017-plugin-content-mirror-bridges-apm-to-host-discovery.md

@@ -329,7 +329,9 @@ mirror does carry, and is reported.
   stands; this ADR fixes the second, previously-unverified half.
 - `CONTEXT.md`'s "Plugin" and "Plugin marketplace" glossary entries are updated to describe the
   flat mirror as a second compiled-output category, alongside the existing
-  `.claude-plugin/plugin.json`/`marketplace.json` description.
+  `.claude-plugin/plugin.json`/`marketplace.json` description. Superseded 2026-08-17: CONTEXT.md was
+  cut back to one-line definitions and no longer describes either compiled-output category;
+  `docs/spec/architecture.md` is where the mirror is documented.
 - A future apm release that ships a native `.apm/`-aware plugin.json compiler (closing this gap
   upstream) would let `sync-plugin-content.sh` and its drift gate be deleted outright — nothing in
   this ADR's decision depends on the flat mirror existing beyond satisfying the current installer's