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>

scripts/resolvers/preamble/generate-writing-style-migration.ts

@@ -0,0 +1,26 @@
+import type { TemplateContext } from '../types';
+
+export function generateWritingStyleMigration(ctx: TemplateContext): string {
+  return `If \`WRITING_STYLE_PENDING\` is \`yes\`: You're on the first skill run after upgrading
+to gstack v1. Ask the user once about the new default writing style. Use AskUserQuestion:
+
+> v1 prompts = simpler. Technical terms get a one-sentence gloss on first use,
+> questions are framed in outcome terms, sentences are shorter.
+>
+> Keep the new default, or prefer the older tighter prose?
+
+Options:
+- A) Keep the new default (recommended — good writing helps everyone)
+- B) Restore V0 prose — set \`explain_level: terse\`
+
+If A: leave \`explain_level\` unset (defaults to \`default\`).
+If B: run \`${ctx.paths.binDir}/gstack-config set explain_level terse\`.
+
+Always run (regardless of choice):
+\`\`\`bash
+rm -f ~/.gstack/.writing-style-prompt-pending
+touch ~/.gstack/.writing-style-prompted
+\`\`\`
+
+This only happens once. If \`WRITING_STYLE_PENDING\` is \`no\`, skip this entirely.`;
+}

scripts/resolvers/preamble/generate-writing-style.ts

@@ -0,0 +1,38 @@
+import * as fs from 'fs';
+import * as path from 'path';
+import type { TemplateContext } from '../types';
+
+function loadJargonList(): string[] {
+  const jargonPath = path.join(__dirname, '..', '..', 'jargon-list.json');
+  try {
+    const raw = fs.readFileSync(jargonPath, 'utf-8');
+    const data = JSON.parse(raw);
+    if (Array.isArray(data?.terms)) return data.terms.filter((t: unknown): t is string => typeof t === 'string');
+  } catch {
+    // Missing or malformed: fall back to empty list. Writing Style block still fires,
+    // but with no terms to gloss — graceful degradation.
+  }
+  return [];
+}
+
+export function generateWritingStyle(_ctx: TemplateContext): string {
+  const terms = loadJargonList();
+  const jargonBlock = terms.length > 0
+    ? `**Jargon list** (gloss each on first use per skill invocation, if the term appears in your output):\n\n${terms.map(t => `- ${t}`).join('\n')}\n\nTerms not on this list are assumed plain-English enough.`
+    : `**Jargon list:** (not loaded — \`scripts/jargon-list.json\` missing or malformed). Skip the jargon-gloss rule until the list is restored.`;
+
+  return `## Writing Style (skip entirely if \`EXPLAIN_LEVEL: terse\` appears in the preamble echo OR the user's current message explicitly requests terse / no-explanations output)
+
+These rules apply to every AskUserQuestion, every response you write to the user, and every review finding. They compose with the AskUserQuestion Format section above: Format = *how* a question is structured; Writing Style = *the prose quality of the content inside it*.
+
+1. **Jargon gets a one-sentence gloss on first use per skill invocation.** Even if the user's own prompt already contained the term — users often paste jargon from someone else's plan. Gloss unconditionally on first use. No cross-invocation memory: a new skill fire is a new first-use opportunity. Example: "race condition (two things happen at the same time and step on each other)".
+2. **Frame questions in outcome terms, not implementation terms.** Bad: "Is this endpoint idempotent?" Good: "If someone double-clicks the button, is it OK for the action to run twice?" Ask the question the user would actually want to answer.
+3. **Short sentences. Concrete nouns. Active voice.** Standard advice from any good writing guide. Prefer "the cache stores the result for 60s" over "results will have been cached for a period of 60s."
+4. **Close every decision with user impact.** Connect the technical call back to who's affected. "If we skip this, your users will see a 3-second spinner on every page load." Make the user's user real.
+5. **User-turn override.** If the user's current message says "be terse" / "no explanations" / "brutally honest, just the answer" / similar, skip this entire Writing Style block for your next response, regardless of config. User's in-turn request wins.
+6. **Glossary boundary is the curated list.** Terms below get glossed. Terms not on the list are assumed plain-English enough. If you see a term that genuinely needs glossing but isn't listed, note it (once) in your response so it can be added via PR.
+
+${jargonBlock}
+
+Terse mode (EXPLAIN_LEVEL: terse): skip this entire section. Emit output in V0 prose style — no glosses, no outcome-framing layer, shorter responses. Power users who know the terms get tighter output this way.`;
+}