docs(readme,skills): the cold-start "start here" map carries --max-tokens=3000, gated (P15)

Capture-audit round 2026-09-04, finding P15: a bare `ripwire <dir>` is 13% of observed agent calls
and the commonest first call of a session, at est_tokens="8990" (22,275 B) on this checkout, where
`--max-tokens=3000` serves the head of the same ranking at 2,519. Owner call: the binary's default
stays as it is (dozens of gates parse the bare map); the guidance moves.

Lane L0 found src/wrap.h's paste block and every skills/*/SKILL.md already budgeted. A repo-wide sweep
found the pattern in three remaining places, all fixed here:

- README.md "Four commands worth learning first": `ripwire .` → `ripwire . --max-tokens=3000`,
  the comment disclosing both sizes (bytes and est_tokens, approximate so it cannot pin a figure
  that moves with every commit).
- README.md build-from-source block: the same line in its `./build/` spelling.
- skills/ripwire-efficient/compress-ladder.md rung 0: the map rung now names the budget.

Deliberately untouched: the determinism / xmllint gate lines in CLAUDE.md, CONTRIBUTING.md,
AGENTS.md and the opt-remarks skill (those are gates, not a start-here recommendation, and the
bare map is what they must diff); README's savings-ledger row for "Orient me in this repo" and its
EVALS §5 twin (a measurement reproduced by the command in its row — changing the command voids
the measured number); `analyze` ↔ `ripwire <dir>` in the MCP skill's verb table (an equivalence,
not advice).

Gate, RED-first: test/readmedriftcheck.sh grows arm (G), the cold-start arm — (G1) presence guard
on README's "start here" idiom, (G2) no start-here invocation may be bare, (G3) mutation control
(the budget flag stripped from a copy is caught), (G4) the promise arm: both maps re-run with
--no-cache, the budgeted map must be a non-empty SUBSET of the bare map's rows with est_tokens
≤ 4,500 while the bare map sits above it. G2 and G4 were red on the unedited README; the whole
gate is green after the edit (bare=8990 budgeted=2519 rows=38/184).

Co-Authored-By: Claude Fable 5.1 <noreply@anthropic.com>