feat: add no-unrestricted-loop-in-serverless lint rule

[danielchen0]

Summary

• Adds no-unrestricted-loop-in-serverless rule that detects unbounded loops (while(true), for(;;), while(1)) without a break or return in the loop body
• These loops cause Vercel 300s timeouts in serverless functions — 21K+ timeouts/week in production
• Smart about scope: doesn't count break inside nested loops/switches, or return inside nested arrow functions (e.g. .map() callbacks)
• Allows loops that have proper exit conditions (break, return, bounded test)
• Platform: backend only

Test plan

Scenario	Expected
while (true) { await fetchData(); } (no break)	Error flagged
for (;;) { await poll(); } (no break)	Error flagged
while (1) { doWork(); } (no break)	Error flagged
while (true) { if (done) break; }	No error
while (true) { if (done) return data; }	No error
for (let i = 0; i < 100; i++) { ... }	No error
while (count < 10) { ... }	No error
while (true) { for (...) { break; } } (break in nested loop)	Error flagged (break doesn't exit outer)
while (true) { data.map(x => { return x; }) } (return in nested fn)	Error flagged (return doesn't exit loop)

[daniel-chen-1]

Pushed an auto-fix commit to unblock the failing Lint & Format check (eslint @typescript-eslint/no-unnecessary-boolean-literal-compare in src/rules/no-unrestricted-loop-in-serverless.ts). CI should re-run shortly.

[lainterr]

Reviewed as steward. Approving — well-scoped.

Correctly handles:

• while (true), while (1), for (;;), for (; true; )
• hasBreakOrReturn walks up to confirm break/return belongs to this loop and not a nested loop or function

Non-blocking notes:

1. do { ... } while (true) is not caught. Easy add — same hasBreakOrReturn check with a DoWhileStatement visitor.

2. throw is not counted as a termination path. A loop that exits via throw new Error(...) will be flagged but is in fact bounded. Probably acceptable since throw-as-loop-exit is rare and arguably bad style.

3. The platform tag is backend — good. Consider whether long-running web workers or service workers (web platform) deserve coverage too. They're not strictly serverless but unbounded loops there will hang the worker. Could be a follow-up rule with broader scope, since the message specifically says 'serverless' which would be misleading if applied to workers.

OK to ship as-is.

[daniel-chen-1]

Auto-fix: Lint & Format CI was failing on this rebase because README.md needed prettier formatting. Pushed prettier --write README.md as a follow-up commit. CI should go green on the next run.

[daniel-chen-1]

Rebased onto main after #51 merged — the conflicts were mechanical (rule-registration list, README rule table, rule-count assertion, meta.ts platform map), no logic touched. New head is 7b6e531, all 7 CI checks green, mergeable=true. Ready to merge when you are.