docs(rfc): define and enforce a uniform RFC format; adopt it across the corpus

Define the in-file RFC contract in docs/rfc/README.md § The file format:
the header block (`# RFC: <title>` plus a dateless Status enum
cross-checked against the lifecycle folder), the per-lifecycle body
skeleton (a Problem opener everywhere; Proposal/Alternatives considered/
Acceptance criteria/Risks in proposed/; present-tense Decision/
Consequences with proposal-era headings banned in implemented/; the
frozen proposal shape in rejected/), and a mandatory Alternatives
considered section with a date-fenced grandfather comment for pre-format
RFCs whose alternatives are not reconstructible from the record.

Enforce it with a new doc-sync gate, scripts/verify-rfc-format.ts, and
normalize all 112 RFCs to it: ~15 Status-line spellings collapse to the
enum, 29 Context openers become Problem, the 39 legacy-format XXX debt
markers are resolved and banned from reappearing, proposal-era sections
in implemented RFCs are rewritten to shipped reality (including the
web/fs/subagent seam RFCs' migration plans and test checklists, closing
the doc-tiers deferred-work item on the web seam), every RFC gains an
Alternatives considered section or the grandfather comment, and the
bilingual pair is re-mirrored and re-recorded.

Move the generated index tables out of README.md into a fully generated
docs/rfc/INDEX.md — gen-rfc-index now writes the whole file, and
verify-rfc-classification checks its freshness and rejects index-shaped
rows in the curated README — which makes room for the format contract to
live in the README front door instead of a separate FORMAT.md.

The decision record, and the first RFC written in the new format, is
docs/rfc/implemented/process/2026-07-05-uniform-rfc-format.md.

docs/rfc/proposed/process/2026-06-11-supply-chain-and-vendor-drift.md

@@ -2,8 +2,6 @@
 
 Status: proposed
 
-<!-- XXX: legacy ADR/RFC body format, not yet normalized to a unified RFC template. -->
-
 ## Problem
 
 The vendor manifest ([the vendoring decision](../../implemented/process/2026-06-11-vendor-cordis-as-source.md)) is enforced at commit time in the *forward* direction (vendored change ⇒ manifest update) but nothing verifies the manifest's *claims*: that vendor/ actually equals upstream-at-SHA plus exactly the logged modifications. And the handful of true npm dependencies have no advisory monitoring or update cadence.
@@ -19,6 +17,17 @@ The vendor manifest ([the vendoring decision](../../implemented/process/2026-06-
 
 3 is trivial — do first. 1 requires network access from CI to the upstream repos (private — needs a token) and converting the two existing logged modifications into patch files. 2 and 4 are config.
 
+## Alternatives considered
+
+- **`pnpm audit` instead of osv-scanner** — either satisfies the advisory-scanning shape; the choice is deferred to implementation.
+- **A scheduled agent task instead of Renovate** — equivalent for proposing small update PRs that ride the full gate suite; vendored packages stay excluded either way (their updates follow the manifest sync procedure).
+
+## Acceptance criteria
+
+- The license inventory script runs in CI and fails on a missing LICENSE or a `license` field that contradicts the inventory in `vendor/README.md`.
+- The nightly drift job reconstructs `vendor/` from the manifest SHAs plus checked-in patch files and fails on any unexplained diff.
+- Advisory scanning runs on the lockfile on schedule and on lockfile-touching PRs.
+
 ## Risks
 
 Upstream repos are private mirrors; CI credentials and availability are the main friction for the drift check. If blocked, run it as a local scheduled agent task instead of CI.