Security: second ReDoS sweep (unauthenticated email check first; request path, docs Worker, lazy scans) #174

Second ReDoS sweep. These were found while verifying #173 (the #168 follow-ups). All of them predate #173. The first item is reachable without authentication; fix it before 0.6.5.

Must fix (unauthenticated, CPU per request)

1. Email check runs before the length cap. packages/api/src/routes/password-reset.ts:123 (unauthenticated POST /request) and packages/api/src/routes/invites.ts:213 run EMAIL = /^[^\s@]+@[^\s@]+\.[^\s@]+$/ (invites.ts:85) before checking email.length > 254. The domain part is ambiguous on dots, so "a@" + ".".repeat(n) + "@" backtracks in O(n²). jsonBody (packages/api/src/tokens.ts:41) has no size cap, so one request with a 100k-character email costs seconds of CPU. That kills the Worker on its CPU limit, or stalls the event loop on Node/Docker. limitPublic limits how often a client can call, not how much each call costs.
   • Fix: check the length first in both places (Studio's roles.ts:341 already does). Make EMAIL linear: a single @, then an indexOf check for the dot.
   • Fix: add a body size cap to jsonBody (for example 64 KiB; return 413 above it) for the public token routes.
   • Tests: a 100k adversarial input completes in well under 100 ms, and an oversized body gets 413.

Should fix (request path or agent input)

2. packages/core-ts/src/redirects.ts:20 normalisePath runs /\/+$/ on every site request (astro-renderer routing.ts:167, taxonomy.ts:1327 redirectFor). Astro collapses duplicate slashes first, which mitigates it, but the result also feeds ancestorPaths, which is O(n²) in memory on runs of slashes. Use a linear trim. Do the same for joinTarget (redirects.ts:36) and packages/schedules/src/feed-check.ts:217 urlPath.

3. apps/docs/src/worker/paths.ts:42: isPagePath = !/\.[^/]*$/.test(pathname) runs on every docs Worker GET. "/" + ".".repeat(n) + "/" is O(n²), about 150 ms at 16 KB. Use a lastIndexOf check.

4. Lazy scans that rescan to the end when the closer is missing, all on agent, editor or upload input:

   • packages/core-ts/src/search-rows.ts:43 (fenced code at publish time)
   • packages/core-ts/src/media/svg.ts:144 (/\/\*[\s\S]*?\*\//g on uploaded SVG CSS)
   • packages/schedules/src/feed-check.ts:157 and :202
   • packages/core-ts/src/automations.ts:450

   For each one, measure with an adversarial input. Rewrite the ones that are superlinear with indexOf-based scanners.

5. packages/agent-runtime/src/skills.ts:39 /^\s+([^:]+):\s*(.*)$/: \s+ overlaps [^:]+, so a line of only spaces is O(n²). Check whether skill markdown can come from callers. Fix it either way, it is cheap.

6. packages/ui/src/blocks/editor/markdown-blocks.ts:69,76 /\n*$/: client-side, but a body written by an agent can reach it. Use a linear trim.

Done when

• Every rewrite has an equivalence test against the old regex on normal inputs and a 100k-character adversarial case.
• A short CONTRIBUTING or AGENTS.md note: avoid unanchored or end-anchored quantified runs and lazy scans on external input, and prefer indexOf scanners.
• Patch changesets for the published packages touched.