feat(skills): third-party web-actions contract — offer to drive vendor-site steps, never just dump a manual list

When a workflow needs something done on an external website the user
controls (register an API key, create a vendor account, configure a
dashboard/webhook/OAuth app), five skills (ship, spec, office-hours,
setup-deploy, land-and-deploy) now follow one contract: offer to drive it
in a visible browser via gstack's own stack ($B headed + handoff/resume,
GStack Browser) behind ONE per-task consent question naming the exact site
and actions; passwords, payment, CAPTCHA, and identity stay user-performed;
captured secrets go to owner-only files or the user's secret store, never
chat/logs/history; and the credential is verified with one non-mutating API
call before any success claim — dashboards show masked placeholders, and a
401 catches them. Declining yields manual steps and a blocked-on-user mark;
nothing new is ever installed to close the gap.

New resolver token {{THIRD_PARTY_ACTIONS}} (adapted from the fork's
contract — their Aside-browser detection swapped for our own driver stack;
MIT portions noted). Parity guards bumped with growth itemized (ship
1.10->1.12 at measured 1.103x; office-hours skeleton 101K / 1.09 at
measured 1.079x); ship goldens refreshed.

Ported from time-attack/gstack (GStack 2), driver adaptation ours.

Co-authored-by: Sina Matian <sina@time-attack.dev>
Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

scripts/resolvers/index.ts

@@ -36,12 +36,14 @@ import { generateMakePdfSetup } from './make-pdf';
 import { generateTasksSectionEmit, generateTasksSectionAggregate } from './tasks-section';
 import { SECTION, SECTION_INDEX } from './sections';
 import { generateRedactTaxonomyTable, generateRedactInvocationBlock } from './redact-doc';
+import { generateThirdPartyActions } from './third-party-actions';
 
 export const RESOLVERS: Record<string, ResolverValue> = {
   SLUG_EVAL: generateSlugEval,
   SLUG_SETUP: generateSlugSetup,
   REDACT_TAXONOMY_TABLE: generateRedactTaxonomyTable,
   REDACT_INVOCATION_BLOCK: generateRedactInvocationBlock,
+  THIRD_PARTY_ACTIONS: generateThirdPartyActions,
   COMMAND_REFERENCE: generateCommandReference,
   SNAPSHOT_FLAGS: generateSnapshotFlags,
   PREAMBLE: generatePreamble,