test(e2e): bump harness defaults for CI; raise workflow timeouts

Round 3 CI tuning. Previous rounds bumped tests one-at-a-time; this round
moves the budgets into the harness defaults so all tests benefit equally
without per-test churn.

Harness default changes:
  - waitForReady() in opencode-runner/spawn.ts:    30s → 120s
  - sendPrompt() default in harness.ts:            30s → 180s
  - waitFor() default in harness.ts:               10s → 60s
  - sendPrompt() default in pi-harness.ts:         60s → 180s
  - waitFor() default in pi-harness.ts:            10s → 60s

Workflow changes:
  - per-test Bun --timeout: 300s → 600s (both host jobs in ci.yml & release.yml)
  - host job timeout-minutes: 20-25 → 40 (to cover 600s × multiple slow tests)

GitHub-hosted ubuntu runners take ~3-5x longer than local hardware for any
operation involving subprocess spawn (opencode serve, pi --print) + HTTP
roundtrip to the mock provider. The previous per-test bumps still hit the
limits because cold-start cost wasn't budgeted into the harness defaults.

No production code changes. Individual tests can still pass smaller
timeoutMs values to override these defaults locally.