merge: origin/main v1.0.0.0 into garrytan/fix-checkpoints

Main shipped the v1 prompts rewrite (simpler writing style + real LOC
receipts + /plan-tune observational substrate). Resolved conflicts:

- VERSION / package.json: bumped 0.18.5.0 → 1.0.1.0 (main is 1.0.0.0,
  this branch lands next).
- CHANGELOG: moved the /context-save + /context-restore entry to the
  top as v1.0.1.0, above main's v1.0.0.0. Also removed the em-dash
  variants in the new entry (ship voice rule).
- TODOS: kept both sections — Context skills (lane feature TODO) first,
  main's PACING_UPDATES_V0 + Plan Tune v2 deferrals below.
- Migration: renamed gstack-upgrade/migrations/v0.18.5.0.sh →
  v1.0.1.0.sh (matches new version). Test path updated.

preamble.ts auto-merged cleanly: main's question-tuning, explain_level,
and writing-style sections composed with my context-save/context-restore
routing rule.

All SKILL.md files regenerated via `bun run gen:skill-docs --host all`
per CLAUDE.md's "never resolve generated files by accepting either
side" rule. Golden fixtures (claude/codex/factory ship) also regenerated.

bun test: 0 failures.

test/helpers/touchfiles.ts

@@ -79,6 +79,9 @@ export const E2E_TOUCHFILES: Record<string, string[]> = {
   'plan-eng-review-artifact':  ['plan-eng-review/**'],
   'plan-review-report':        ['plan-eng-review/**', 'scripts/gen-skill-docs.ts'],
 
+  // /plan-tune (v1 observational)
+  'plan-tune-inspect':         ['plan-tune/**', 'scripts/question-registry.ts', 'scripts/psychographic-signals.ts', 'scripts/one-way-doors.ts', 'bin/gstack-question-log', 'bin/gstack-question-preference', 'bin/gstack-developer-profile'],
+
   // Codex offering verification
   'codex-offered-office-hours':  ['office-hours/**', 'scripts/gen-skill-docs.ts'],
   'codex-offered-ceo-review':    ['plan-ceo-review/**', 'scripts/gen-skill-docs.ts'],
@@ -241,6 +244,9 @@ export const E2E_TIERS: Record<string, 'gate' | 'periodic'> = {
   'plan-eng-coverage-audit': 'gate',
   'plan-review-report': 'gate',
 
+  // /plan-tune — gate (core v1 DX promise: plain-English intent routing)
+  'plan-tune-inspect': 'gate',
+
   // Codex offering verification
   'codex-offered-office-hours': 'gate',
   'codex-offered-ceo-review': 'gate',