Expose per-agent schedule and trigger in the control panel (WI-046)

[nateshpp]

What this PR does

Makes every agent's model, runner, schedule, and trigger settable from one operator surface: the control panel's Agents tab. Choosing when and how an agent fires is now a panel setting rather than a hand-edit of .modonome/config.yaml. Closes WI-046.

Stacked on #125 (base is feature/configurable-trigger-layer, since it uses the schedule/trigger schema fields that PR added). Merge #125 first, then this rebases onto main.

• apps/control-panel/src/state/types.ts: the role type gains schedule ({cron, timezone?}) and trigger becomes the string-or-object union WI-032 defined.
• apps/control-panel/src/screens/SettingsScreen.tsx: the Agents tab adds a schedule cron input, a trigger type select (with a hint), and a conditional after-role list, plus immutable update handlers that clear an emptied field instead of saving an invalid empty value. Control density stays within the coherence budget (7 of 10).
• tests/schedule-trigger-schema.test.mjs: the role sub-schema accepts a schedule, a bare string trigger, and an after-role object, and rejects a bad trigger.type or an unknown trigger sub-key.

Governance checklist

• npm run verify passes through every governance gate (control-panel coherence and coverage included) and AgentProof (25/25). It stops only at check:frontend/npm test on missing dev deps (esbuild, js-yaml) that CI installs; the panel's own typecheck/vitest run in CI where those deps are present.
• No em dashes in any tracked file
• Prose states conclusions directly
• No AI co-author lines in commit messages
• Ratchet logic unchanged (n/a)
• No new AgentProof scenario (n/a)
• Config schema unchanged in this PR (the fields were added in Configurable trigger and schedule layer (WI-032) #125; no schema_version change)
• Prompt unchanged (n/a)

Test evidence

$ node --test tests/schedule-trigger-schema.test.mjs
# tests 5
# pass 5
# fail 0

$ node scripts/check-control-panel-coherence.mjs
PASS: every screen is within the control-density budget and every lever has a hint.

$ node scripts/check-control-panel-coverage.mjs
PASS: every config lever is either exposed or documented as intentionally not.