merge: integrate origin/main (v1.1.0.0) — V1 + Puppeteer parity + /plan-tune

Big merge. Main shipped three releases while this branch was in flight:
- v0.19.0.0 /plan-tune skill (observational layer; dual-track dev profile)
- v1.0.0.0 V1 prompts (simpler, outcome-framed, jargon-glossed) + LOC receipts
- v1.1.0.0 browse Puppeteer parity (load-html, file://, --selector, --scale)

This branch bumps to v1.2.0.0 (above main's v1.1.0.0) per the
branch-scoped-version rule in CLAUDE.md. My "0.19.0.0" CHANGELOG entry
is renamed to "1.2.0.0" and dated 2026-04-18 to land above main's trail.

Conflicts resolved:
- VERSION / package.json: 1.2.0.0
- CHANGELOG.md: preserved my entry at top (renamed), kept main's 1.1.0.0
  / 1.0.0.0 / 0.19.0.0 / 0.18.4.0 trail below in correct order
- .github/docker/Dockerfile.ci: kept my xz-utils + nodejs.org tarball
  fix (real CI bug fix main didn't have); absorbed main's retry loop
  structure for both apt and the tarball curl
- bin/gstack-config: kept both my checkpoint_mode/push section and
  main's explain_level writing-style section
- scripts/resolvers/preamble.ts: kept my submodule refactor as the
  file shape; extracted main's new generateWritingStyle and
  generateWritingStyleMigration into scripts/resolvers/preamble/
  submodules; absorbed main's generateQuestionTuning import
- All generated SKILL.md files: resolved by regen via
  bun run gen:skill-docs --host all (per CLAUDE.md: never hand-merge
  generated files — resolve templates and regen)
- Ship golden fixtures (claude/codex/factory): refreshed

Tier 2 preamble composition now includes all 8 sections: context
recovery, ask-user-format, writing-style, completeness, confusion,
continuous checkpoint, context health, question tuning.

Main also brought new test files from /plan-tune: skill-e2e-plan-tune,
upgrade-migration-v1, v0-dormancy, writing-style-resolver. All absorbed.
468 tests pass.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

CLAUDE.md

@@ -185,6 +185,18 @@ Rules:
 - **Express conditionals as English.** Instead of nested `if/elif/else` in bash,
   write numbered decision steps: "1. If X, do Y. 2. Otherwise, do Z."
 
+## Writing style (V1)
+
+Default output from every tier-≥2 skill follows the Writing Style section in
+`scripts/resolvers/preamble.ts`: jargon glossed on first use (curated list in
+`scripts/jargon-list.json`, baked at gen-skill-docs time), questions framed in
+outcome terms ("what breaks for your users if...") not implementation terms,
+short sentences, decisions close with user impact. Power users who want the
+tighter V0 prose set `gstack-config set explain_level terse` (binary switch,
+no middle mode). See `docs/designs/PLAN_TUNING_V1.md` for the full design
+rationale. The review pacing overhaul that originally tried to ride alongside
+writing-style was extracted to V1.1 — see `docs/designs/PACING_UPDATES_V0.md`.
+
 ## Browser interaction
 
 When you need to interact with a browser (QA, dogfooding, cookie setup), use the