closeout: pre-publish PR-body validation + context-aware pr-contract parser

[ArchonVII]

Part of the PR-closeout contract repair (forensic analysis of session 019eccc1).

GW-A — the keystone slice in github-workflows:

• Add a --body-file <path|-> (stdin) input mode to scripts/pr-contract.mjs so the SAME validator can run on a drafted body before a PR exists, not only against a remote PR. Removes the push -> create -> amend -> re-scan loop (F2/F3).
• Make the parser context-aware (still strict): mask HTML comments before the placeholder scan (so a template's own instructional comment no longer trips it, F4) and mask fenced/inline code + quoted/blockquoted text before the generic-verification scan on free prose (so an explanatory note citing a command isn't rejected, F7). Checked checkbox claims and evidence-field placeholders still hard-fail.
• Add --help/usage to pr-contract.mjs, agent-pr-ready.mjs, agent-close-preflight.mjs (F-DISC).
• Acceptance-table fixtures, including the "still fails" cases.

Follow-ups (separate slices): retag @v1; repo-template vendor + parity guard + close-scan Windows fix (RT-A); gate-label audit + ci:full seed (GW-B); trivial-edit lanes (RT-B).

[ArchonVII]

Delivered. Verified firsthand on main @ 85cf6fa (2026-07-01):

• --body-file <path|-> pre-publish mode + context-aware parser (HTML-comment masking before the placeholder scan, code/quote masking before the generic-verification scan): landed in f0dbb3c (PR feat(pr-contract): add --body-file pre-publish mode and context-aware parser #82) and a76183f (PR fix(pr-contract): relax marker prose guard #91).
• --help/usage (F-DISC): present in scripts/pr-contract.mjs (printUsage(), lines ~473-557) and in scripts/agent-pr-ready.mjs + scripts/agent-close-preflight.mjs.
• Acceptance fixtures: scripts/fixtures/ + scripts/pr-contract.test.mjs.
• Suite re-run: npm test → vitest 9 files / 159 tests / 159 pass.

Named follow-up slices are tracked separately: RT-A (repo-template re-vendor + parity guard) is being executed now under the 2026-07-01 friction arc; GW-B is #83; @v1 retag rides the next parser change (substance-only contract) from the same arc.