v0.0.1.0 chore: scaffold Hình Học Sống (Astro + GitHub Pages) (#1)

* chore: add gstack skill routing rules to CLAUDE.md

Append a "## Skill routing" section so future Claude Code sessions in this repo route
each task through the matching gstack skill (e.g., /investigate for bugs, /ship for PRs,
/office-hours for product brainstorming).

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

* chore: scaffold Astro 5 + TypeScript strict with base /try-gstack/

Initialize the project per the autoplan-locked decisions:
- Astro 5 SSG, output static, base path /try-gstack/ for GitHub Pages subdirectory hosting
- TypeScript strict (Astro's strict tsconfig + path alias ~/* -> src/*)
- @astrojs/sitemap for SEO meta
- bun as the package manager (lockfile committed)

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

* feat: Vietnamese landing page with Be Vietnam Pro + i18n stub

Implement the locked design decisions D2 (typography) and D3 (palette) plus the i18n
discipline from autoplan eng review:
- Be Vietnam Pro single family (woff2, weights 400/500/700, vietnamese subset) self-hosted
  via @fontsource so KaTeX/CDN-blocking ISPs cannot break the page
- font-feature-settings: "kern", "locl" for proper VN diacritic positioning
- 17px body / 1.6 line-height / max-w-prose 56ch (denser than English)
- 3-color SGK-aligned palette in tailwind config: pair1 #D7263D, pair2 #1B998B, pair3 #F46036
- BaseLayout with lang="vi", canonical URL, OpenGraph (vi_VN), X-Frame-Options DENY
- src/i18n/vi.ts holds every user-facing string; t() helper resolves the active locale.
  Adding English later means adding en.ts; no string churn through templates.
- Landing page lists three grade cards with "Sắp ra mắt" status (modules ship later)

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

* test: bootstrap Vitest with pure geom-engine vec module

Establish the math-engine boundary and test discipline from autoplan eng decision E2:
- src/geom-engine/ is pure (no DOM imports allowed); first module is vec.ts
- Vec2 helpers: vec, add, sub, scale, dot, len, dist, normalize, approxEqualLen
- EPSILON_LEN=0.5 viewBox units justified vs ~4px human drag precision
- scale() normalizes IEEE-754 -0 back to +0 so consumers don't see signed-zero ghosts
- Vitest config gates the module at 95% line/function/statement, 90% branch
- 16 unit tests covering commutativity, mutation safety, orthogonality, normalization,
  and EPSILON tolerance behavior

Property tests via fast-check come with the first canvas module; this commit establishes
the test scaffold so adding them later is one dependency away.

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

* ci: GitHub Actions test workflow + Pages deploy via deploy-pages@v4

Wire the autoplan-locked CI/CD pipeline (decision E3) for GitHub Pages hosting:
- ci.yml: typecheck + tests + build on every PR and push to main
- deploy.yml: build + actions/deploy-pages@v4 on push to main, concurrency-grouped
  so a force-push retry doesn't abort an in-flight rollback
- Build env pins SITE_URL=https://tiennm99.github.io and SITE_BASE=/try-gstack so
  astro.config.mjs produces correct canonical/OG URLs against the subdirectory host
- bun 1.3.13 pinned for both workflows

Lighthouse-CI + size-limit gates deferred until the first canvas module ships
(no JS bundle to budget yet — current pages are zero-JS).

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

* chore: VERSION 0.0.1.0 + CHANGELOG + RUNBOOK + README rewrite

Initial 4-digit gstack version (matches package.json), changelog entry for the scaffold,
operations runbook covering rollback and the deferred .vn domain trigger (500 sessions/30d
OR 1 organic teacher share OR 5+ modules shipped). README rewritten as the project README
for Hình Học Sống with the locked architectural decisions visible to teammates.

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

* chore: TODOS.md tracking deferred autoplan items

Capture the deferred work surfaced by the /office-hours + /autoplan reviews so the
backlog is visible to teammates and bisectable from the source-of-truth design doc.
Organized by component (Phase 0 distribution, TheoremCanvas, Module 3/1/2, testing
infrastructure, retention, domain) then priority P0–P4. Per the gstack TODOS.md
format conventions.

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

---------

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

.github/workflows/ci.yml

@@ -0,0 +1,33 @@
+name: CI
+
+on:
+  pull_request:
+  push:
+    branches:
+      - main
+
+permissions:
+  contents: read
+
+jobs:
+  ci:
+    runs-on: ubuntu-latest
+    steps:
+      - uses: actions/checkout@v4
+
+      - name: Setup Bun
+        uses: oven-sh/setup-bun@v2
+        with:
+          bun-version: 1.3.13
+
+      - name: Install dependencies
+        run: bun install --frozen-lockfile
+
+      - name: Typecheck
+        run: bun run typecheck
+
+      - name: Unit tests
+        run: bun run test
+
+      - name: Build
+        run: bun run build

.github/workflows/deploy.yml

@@ -0,0 +1,52 @@
+name: Deploy to GitHub Pages
+
+on:
+  push:
+    branches:
+      - main
+  workflow_dispatch:
+
+permissions:
+  contents: read
+  pages: write
+  id-token: write
+
+concurrency:
+  group: pages-deploy
+  cancel-in-progress: false
+
+jobs:
+  build:
+    runs-on: ubuntu-latest
+    steps:
+      - uses: actions/checkout@v4
+
+      - name: Setup Bun
+        uses: oven-sh/setup-bun@v2
+        with:
+          bun-version: 1.3.13
+
+      - name: Install dependencies
+        run: bun install --frozen-lockfile
+
+      - name: Build
+        run: bun run build
+        env:
+          SITE_URL: https://tiennm99.github.io
+          SITE_BASE: /try-gstack
+
+      - name: Upload artifact
+        uses: actions/upload-pages-artifact@v3
+        with:
+          path: ./dist
+
+  deploy:
+    needs: build
+    runs-on: ubuntu-latest
+    environment:
+      name: github-pages
+      url: ${{ steps.deployment.outputs.page_url }}
+    steps:
+      - name: Deploy to GitHub Pages
+        id: deployment
+        uses: actions/deploy-pages@v4