feat(server): Bun/TypeScript re-implementation of PR review engine

Reimplements the pr_agent review pipeline (previously Python package) in
Bun/TypeScript, verified end-to-end against a real GitHub App + 9router:

- src/diff.ts: git patch processing (extend_patch, line-numbered hunks,
  token-budget generate_full_patch, generated/invalid file filters)
- src/review.ts: orchestrator (fetch PR/diff -> render prompts -> LLM ->
  YAML parse -> markdown render -> publish), fallback models
- src/github.ts: GitHub App auth via @octokit/auth-app (JWT -> installation
  token, custom authStrategy for Bun), PR/diff/languages/comments REST
- src/prompts.ts: verbatim pr_reviewer_prompts.toml port (nunjucks templates)
- src/yaml.ts: resilient load_yaml with 9 fallback fixers
- src/markdown.ts: convert_to_markdown_v2 port ('PR Reviewer Guide' comment)
- src/llm.ts: 9router OpenAI-compatible chat completions (non-stream,
  temp omitted for claude-opus-5), timeout 600s
- src/token.ts: js-tiktoken o200k counting
- src/index.ts: webhook server (HMAC verify, segment analytics, /health,
  /api/metrics) + cli.ts one-shot review
- e2e.ts: real-world harness (bun e2e --repo o/r --pr N [--publish])

Verified: bun test 13/13, tsc clean, E2E published a real review comment
(## PR Reviewer Guide) on asepharyana/nextjs-template#19 via GitHub App
MythEclipseBotReview + claude-opus-5 through 9router.

Python run_server.py + pr_agent remain for the live queue worker; server/
is the replacement path.

server/tsconfig.json

@@ -0,0 +1,17 @@
+{
+  "compilerOptions": {
+    "target": "ESNext",
+    "module": "ESNext",
+    "moduleResolution": "bundler",
+    "lib": ["ESNext"],
+    "types": ["bun"],
+    "strict": true,
+    "noEmit": true,
+    "esModuleInterop": true,
+    "skipLibCheck": true,
+    "resolveJsonModule": true,
+    "forceConsistentCasingInFileNames": true,
+    "allowImportingTsExtensions": true
+  },
+  "include": ["src/**/*.ts", "test/**/*.ts"]
+}