docs: 补全 AI 入口/API/路由/现状文档并对齐一致性

新增（Codex 起草，本次纳入并校对）：
- AGENTS.md：仓库级 AI 强约束入口
- docs/00-ai-start-here.md：AI 开发入口与导航
- docs/api.md：账号/生词本/进度 API 合约草案
- docs/routes.md：go-app 页面路由与组件归属
- docs/current-state.md：当前实现状态

补充与对齐：
- 验证命令补 bash（WSL/Linux 为主，PowerShell 为备）：00-ai-start-here、AGENTS
- 04-architecture：新增第六节"项目结构（包布局）"+ 3.2 建表 SQL 草案
- docs/README 导航补 06-tasks；CLAUDE 目录树补 AGENTS/scripts/design_mockups
- 00-ai-start-here 去除已过时的"需要补齐"段
- 06-tasks：Phase 2/3/4/5 交叉引用 api.md / routes.md / 包布局

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

AGENTS.md

@@ -0,0 +1,86 @@
+# AGENTS.md
+
+> Repository-level rules for AI coding agents. Read this before changing files.
+
+## Mission
+
+Build a mobile-first, installable, offline-capable English intensive-listening PWA for "Family Album, U.S.A." using audio plus sentence-synced English subtitles. The MVP is not a video site, social product, generic course platform, or AI speaking scorer.
+
+## Required Reading Order
+
+Before writing code, read these files in order:
+
+1. `docs/00-ai-start-here.md`
+2. `docs/01-vision.md`
+3. `docs/02-requirements.md`
+4. `docs/03-tech-stack.md`
+5. `docs/04-architecture.md`
+6. `docs/05-coding-rules.md`
+7. `docs/06-tasks.md`
+8. `CLAUDE.md`
+
+Use `docs/00-ai-start-here.md` for navigation. Use `docs/05-coding-rules.md` as the hard implementation rulebook.
+
+## Task Discipline
+
+- Work from `docs/06-tasks.md`.
+- Pick only the first `TODO` task whose dependencies are all `DONE`.
+- Do exactly one task per development turn.
+- Mark it `DOING` before implementation, then `DONE` only after its acceptance checks pass.
+- Do not jump ahead, batch multiple tasks, or add V2/V3 scope while doing MVP work.
+
+## MVP Scope
+
+MVP scope is ep1-17 plus these P0 capabilities:
+
+- Course list
+- Audio playback
+- Sentence-synced subtitles
+- Vocabulary notebook
+- Account and cross-device sync
+- PWA install/offline use
+
+Do not implement video playback, line-level Chinese translation, social features, AI speaking scoring, SRS, tests/quizzes, AB repeat, or multi-course logic unless a task explicitly asks for it.
+
+## Technical Constraints
+
+- Frontend: go-app, Go to WebAssembly.
+- Styling: plain CSS files, mobile-first, loaded via go-app handler styles.
+- State: go-app native state and observers.
+- Backend: Go `net/http`.
+- Database: SQLite for user data only.
+- Auth: httpOnly Session Cookie.
+- Deployment target: single self-hosted Go binary serving wasm, static assets, audio, and APIs.
+- Do not add new frameworks, heavy libraries, or third-party dependencies without explicit approval.
+
+## Data Rules
+
+- Content truth source: `family-album-usa/episodes.json`.
+- Do not invent fields. `line` has only `{ "t", "en" }`; there is no `zh`.
+- JSON audio paths such as `/family-album/audio/u0101.mp3` are service paths. Map them to disk under `family-album-usa/audio/`.
+- Do not fabricate audio for ep18-26.
+- `notion_docs/` and `*.bak` are read-only archives. Do not edit, delete, or treat them as source of truth.
+
+## Verification
+
+Before claiming a task is done, run the relevant checks from `docs/05-coding-rules.md` and report exactly what passed or failed.
+
+This project is primarily developed under WSL / Linux (bash). Use bash commands first:
+
+```bash
+GOOS=js GOARCH=wasm go build -o app.wasm   # frontend wasm
+go build                                    # backend
+go vet ./...
+python3 scripts/validate_episodes.py
+```
+
+Windows PowerShell equivalents:
+
+```powershell
+$env:GOOS='js'; $env:GOARCH='wasm'; go build -o app.wasm
+go build
+go vet ./...
+python scripts/validate_episodes.py
+```
+
+Only run the content validator when content data or its schema is touched.