S0308-submodule-agent-doc-budgets: split CLAUDE.md and README.md under their byte budgets

[NSchatz]

Spec: pipeline/active/S0308-submodule-agent-doc-budgets/children/cli.md in the umbrella.

What

CLAUDE.md is always read and measured 23154 bytes against a 16200 byte ceiling. README.md
measured 22693 against 22400. Over budget is a design signal, so the remedy is to split, never to
raise the number and never to delete a line.

Seven whole sections leave CLAUDE.md and two leave README.md, byte for byte, under their existing
headings, into documentation/ (the directory this repo's own agent doc already names for
agent-notes.md and its decision records):

• documentation/repo-gates.md: the docs sidebar and the IA spine, the pre-commit PHI scanner, the
  em-dash brand gate, branch protection, and the attw gate.
• documentation/packaging.md: the published package and the FHIR hole, and hard runtime deps.
• documentation/convert-and-map-codes.md: cosyte convert and cosyte map-codes.

Each reduced document keeps the heading and carries a short pointer at the copy, at the point the
section left. No heading is renamed. Links inside moved text are re-based by exactly one directory,
so every one still resolves and none points outside this repo.

Result

path	before	after	ceiling
CLAUDE.md	23154	11862	16200
README.md	22693	21186	22400

CLAUDE.md is 174 lines and still carries all five headings the estate baseline requires
(## Project, ## Status, ## Tech Stack, ## Engineering Guardrails, ## Standing disciplines).

Evidence

• Heading reachability, per budgeted path, against the base commit: every heading in the old document
  is still reachable from the document that replaced it. Prints nothing for both paths.
• Link resolution over both budgeted paths and all three added files: no absolute link, no link
  outside this repo, no missing target. Prints nothing.
• pnpm test: 777 passed, 41 files. The suite is why redact stayed on the front page:
  test/docs-content.test.ts pins that matrix to README.md, and the first draft that moved it red.
• pnpm check:agent-notes: OK, 26 qualified pointers from 4 files, all resolving.
• pnpm check:no-emdash, pnpm check:no-internal-refs, pnpm format:check, pnpm phi-scan: OK.
• npm pack --dry-run before and after lists the same four entries (CHANGELOG.md, LICENSE,
  README.md, package.json), both with dist/ unbuilt. package.json files is untouched and
  documentation/ is outside it, so the published tarball does not change.