feat(doc-standards): documentation tiers, budgets, and the ceiling gate

Standing docs accrete a paragraph per PR with nothing pushing back; the
root AGENTS.md reached 8,130 words in 50 commits with the same rule
stated two and three times. This encodes the counter-pressure:

- docs/AGENTS.md becomes the documentation standard: the tier taxonomy
  (one home per fact), target word budgets, and the slop checklist.
- verify-doc-budgets joins doc-sync: word ceilings for the six
  accretion-prone standing docs, manifest-driven, frozen at current
  sizes and ratcheted down as each doc is brought to target.
- .agents/skills/dsh-doc-standards: the thin placement/audit/red-gate
  workflow over the standard, mirroring the dsh-translate-docs split.
- RFC (implemented/process) records the decision, alternatives, and
  the first audit cycle's deferred work list.

The gate's first catch was the standard itself (1,057 > 1,000); it
ships condensed to 984 words rather than with a raised ceiling.

docs/development.md

@@ -100,7 +100,8 @@ pnpm run gen-cordis-catalog     # regenerate docs/cordis-catalog/events-and-serv
 pnpm run verify-cordis-catalog  # fail if the cordis events/services catalog is stale
 pnpm run verify-md-wrap  # fail on hard-wrapped prose paragraphs in docs/README markdown
 pnpm run verify-type-equiv  # fail if a ```ts type-equiv doc block drifts from its source type
-pnpm run doc-sync       # doc-typecheck, cordis-catalog freshness, markdown wrap/link, and type-equiv verification
+pnpm run verify-doc-budgets  # fail if a budgeted standing doc exceeds its word ceiling
+pnpm run doc-sync       # all Markdown/doc gates; see the doc-sync script in package.json for the full list
 pnpm run gen-module-graph     # regenerate docs/module-graph.md from package peerDeps
 pnpm run verify-module-graph  # fail if docs/module-graph.md is stale
 pnpm run build          # emit lib/types intermediates, then bundle lib/index.* runtime files