📝 Deduplicate docs into one home per fact

The same facts were restated in up to three files, and the
restatements had already drifted: two claimed timings were 2-5x
off, and the maintain rationale existed in four copies with
different numbers each. Duplicated prose is a liability, not
redundancy.

Each fact now has exactly one owner, with links from the others:

- tool inventory: README § Tooling
- configuration rationale: README § Tooling decisions
- prefix taxonomy: CONTRIBUTING § Script prefix convention
- what runs when and at what cost: CONTRIBUTING § Feedback tiers
- publish procedure: CONTRIBUTING § Publishing workflow

README loses its whole Script prefix convention section and the
Workflows section; CONTRIBUTING loses the Why-these-splits bullets
that repeated the tier table and the rules list. Prose is 23KB to
17KB, with no rule or rationale dropped.

AGENTS.md

@@ -9,9 +9,9 @@ first-action facts. Do not restate evolving prose here — it will drift.
 
 - Project: F#-style pattern matching for TypeScript/ESM. Node `>=26` (pinned via `.node-version`), ESM-only (no CommonJS shim).
 - **While iterating:** `npm run test` (`check:tsc` + the unit suite) for fast feedback on the files you changed.
-- **Definition of done — run this before you call the work finished:** `npm run verify`. It is one shot of the whole-project correctness ladder (`npm run check`: `tsc → oxlint → oxfmt → cspell`, then the unit suite; tsc runs once), excluding advisory maintenance. If all green, commit. If red, look at the output, fix the root cause, and re-run.
-- **On commit:** write a good message (see [CONTRIBUTING.md § Commit messages](./CONTRIBUTING.md#commit-messages)). Lefthook's pre-commit hook already runs the fast, offline, staged-file checks (`tsc` + `oxlint` + `oxfmt` + `cspell`) — don't run them by hand. If the hook fails on style, `npm run fix`, restage, recommit.
-- **`npm run maintain` is NOT part of the feature loop.** `maintain:knip` (dead-code/deps) and `maintain:outdated` (registry) are advisory maintenance scans. Run them only on an explicit maintenance / update-deps branch; CI surfaces them via a non-blocking job, never as a gate.
+- **Definition of done — run this before you call the work finished:** `npm run verify`. If all green, commit. If red, look at the output, fix the root cause, and re-run.
+- **On commit:** write a good message (see [CONTRIBUTING.md § Commit messages](./CONTRIBUTING.md#commit-messages)). Lefthook's pre-commit hook already runs the fast, offline, staged-file checks — don't run them by hand. If the hook fails on style, `npm run fix`, restage, recommit.
+- **`npm run maintain` is NOT part of the feature loop.** Its scans are advisory, never a gate; run them only on an explicit maintenance / update-deps branch.
 
     ```sh
     npm run test    # while iterating (fast feedback)
@@ -37,6 +37,6 @@ Never start a long-lived / blocking process such as `npm run watch`. It runs unt
 - [CONTRIBUTING.md § Rules the tools don't enforce](./CONTRIBUTING.md#rules-the-tools-dont-enforce) — the constraints the linters don't catch; CI/review bounce these. **The most important section.**
 - [CONTRIBUTING.md § Script prefix convention](./CONTRIBUTING.md#script-prefix-convention) — adding an `npm run` script? reuse an existing prefix or it doesn't belong.
 - [CONTRIBUTING.md § Commit messages](./CONTRIBUTING.md#commit-messages) — gitmoji + imperative + 50/72.
-- [CONTRIBUTING.md § Feedback tiers](./CONTRIBUTING.md#feedback-tiers) — what runs when (`watch` / pre-commit / pre-push / `check` / `fix` / CI).
+- [CONTRIBUTING.md § Feedback tiers](./CONTRIBUTING.md#feedback-tiers) — what runs when and at what cost (`watch` / pre-commit / pre-push / `check` / `verify` / `fix` / `maintain` / CI).
 - [README.md § Tooling decisions](./README.md#tooling-decisions) — the rationale behind each tool choice; read before changing tooling.
 - [package.json `#scripts`](./package.json) — the source of truth for every command (the `LEFTHOOK_FILES` convention scopes them to staged files vs. the whole project).