fix(agent): drop unused SessionStatus type and redundant cast

[marcusrbrown]

The local SessionStatus union in src/features/agent/session-poll.ts mirrored what the OpenCode SDK already returns from session.status(). The as SessionStatus | undefined cast on line 173 was structurally redundant — the SDK's inferred type provides the same type === 'idle' / type === 'retry' / type === 'busy' discriminator and narrows the same way.

The new @typescript-eslint/no-unnecessary-type-assertion autofix in @bfra.me/eslint-config@0.51.1 (incoming via Renovate PR #625) correctly flags the cast as redundant and removes it. With the cast gone, the local SessionStatus type becomes unused and trips unused-imports/no-unused-vars (lint error) and TS6196 (build error).

This PR removes both — the unused type and the redundant cast — landing the cleanup on main proactively so Renovate's eslint bump merges without surface conflicts. Tested: full tsc passes, all 1548 tests pass, lint has 0 errors (42 pre-existing non-null-assertion warnings remain, unchanged).

[fro-bot]

Verdict: PASS

The change is correct and well-motivated. The local SessionStatus type was a manual mirror of the SDK's inferred discriminated union, and the as SessionStatus | undefined cast was structurally redundant — the SDK already returns the same shape. Removing both is the right call.

Cast removal (line 165): statuses[sessionId] comes from statusResponse.data, whose type from the SDK already includes the discriminated union members. The downstream narrowing on sessionStatus.type === 'idle' / 'retry' / 'busy' continues to work correctly via the SDK's inferred types. The ESLint rule (no-unnecessary-type-assertion) correctly identified this.

Type removal: With the cast gone the local SessionStatus type had no remaining references, so removing it is correct — keeping it would cause TS6196 and an unused-vars lint error.

No behavioral change; this is a pure type-layer cleanup.

Blocking issues

None

Non-blocking concerns

None

Missing tests

None — no runtime behavior changed; type correctness is validated by tsc passing as noted in the PR description.

Risk assessment (LOW/MED/HIGH): LOW

Single-file, type-only change. Full test suite (1548 tests) and tsc both pass per PR description. No public API impact.

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Run Summary

Field	Value
Event	pull_request
Repository	fro-bot/agent
Run ID	26340599476
Cache	hit
Session	ses_1a9d85e46ffe70M8puosBT69VL