feat: user-reported hard-stool follow-up with deterministic red-flag handoff (#67)

Field finding #67: a hard/lumpy (Bristol 1-2) entry now asks a short follow-up
before saving — difficult to pass, soreness, visible red blood, truly
black/sticky/tarry versus dark brown, and dehydration. Every answer is
user-reported and starts unanswered; nothing is inferred from the photo, and
answering "dark brown" never silently escalates as black stool.

A confirmed red-flag answer writes the same symptom flag manual logging already
uses, so the existing deterministic escalation is the only escalation path.
Mild reports get concise non-diagnostic self-care that states the photo cannot
rule out bleeding, and it is withdrawn whenever a red flag is confirmed.

- src/followup.js: pure follow-up contract (9 unit tests, tests/followup.test.js)
- app.js + styles.css: follow-up block on the safety step for Type 1-2 entries only
- tests/followup.acceptance.mjs: browser acceptance incl. that the AI suggestion
  surface still contains no symptom wording
- CI + release builder gates: npm run test:followup, syntax checks, manifest gate
- scripts/record_release_demo.mjs: records the real follow-up, mild guidance, and
  the black/tarry alert handoff with synthetic data

.gitea/workflows/quality.yml

@@ -54,6 +54,7 @@ jobs:
           npm run test:sleek
           npm run test:manual-fallback
           npm run test:provisional
+          npm run test:followup
       - name: Dependency audit
         run: npm audit --audit-level=high
       - name: Syntax checks