Summary

The stub debt gate (#2353) currently tracks 12 @ts-expect-error suppressions
via .stub-debt-baseline. The gate prevents the count from growing, but the
end goal is zero tolerance: no @ts-expect-error in the scanned directories
at all.

This issue covers the full progression:

1. Fix all existing suppressions — resolve the 12 entries currently
   baselined (6 fork-stub typing mismatches tracked in fix(test): resolve 6 fork-stub typing mismatches in agent-runner e2e test #2352, plus 6 others
   across security.test.ts, profiles.test.ts, integration.test.ts,
   and uuid.test.ts).
2. Set baseline to 0 — decrement .stub-debt-baseline as suppressions
   are removed, reaching 0.
3. Remove the baseline file — delete .stub-debt-baseline entirely.
4. Simplify the gate script — update scripts/check-stub-debt.mjs to
   fail on any @ts-expect-error match (no baseline comparison needed).

Acceptance Criteria

• All 12 @ts-expect-error suppressions resolved (types fixed, not
  replaced with @ts-ignore or any casts)
• .stub-debt-baseline file deleted from the repository
• scripts/check-stub-debt.mjs simplified: scans for @ts-expect-error
  and exits non-zero if any are found (no baseline file read/comparison)
• stub-debt-gate CI job passes with the simplified script
• No regressions in pnpm check or pnpm test

Context

• chore(ci): add stub debt gate (ADR 0005 H5) #2353 introduced the stub debt gate with .stub-debt-baseline = 12
• fix(test): resolve 6 fork-stub typing mismatches in agent-runner e2e test #2352 tracks the 6 fork-stub typing mismatches in
  agent-runner.runreplyagent.e2e.test.ts
• The remaining 6 suppressions are legitimate test guards and test
  infrastructure entries (see inventory in chore(ci): add stub debt gate (ADR 0005 H5) #2353)

Notes

This can be done incrementally — each suppression fix can decrement the
baseline in its own PR. The final PR removes the baseline file and
simplifies the script.