refactor(main): eliminate unsafe runtime cast escapes

Tighten main/runtime dependency contracts to remove non-test `as never` and `as unknown as` usage so type drift surfaces during compile/test checks instead of at runtime.

docs/subagents/agents/opencode-task105-unsafe-casts-20260222T194704Z-zfcm.md

@@ -0,0 +1,78 @@
+# Agent Session: opencode-task105-unsafe-casts-20260222T194704Z-zfcm
+
+- alias: `opencode-task105-unsafe-casts`
+- mission: `Execute TASK-105 eliminate unsafe non-test runtime casts in main boundaries end-to-end without commit.`
+- status: `done`
+- started_utc: `2026-02-22T19:47:35Z`
+- last_update_utc: `2026-02-22T21:56:30Z`
+
+## Intent
+
+- Load TASK-105 context from Backlog MCP and collect exact unsafe cast hotspots.
+- Write implementation plan via writing-plans skill with test-first steps and verification gates.
+- Execute plan with executing-plans skill, parallelizing independent slices where safe.
+
+## Planned Files
+
+- `src/main.ts`
+- `src/main/runtime/**/*.ts`
+- `src/main/**/*.test.ts`
+- `docs/plans/*.md`
+
+## Files Touched
+
+- `docs/subagents/INDEX.md`
+- `docs/subagents/agents/opencode-task105-unsafe-casts-20260222T194704Z-zfcm.md`
+- `docs/subagents/collaboration.md`
+- `docs/plans/2026-02-22-task-105-unsafe-runtime-casts.md`
+- `src/main.ts`
+- `src/main/runtime/app-runtime-main-deps.ts`
+- `src/main/runtime/cli-command-context-main-deps.ts`
+- `src/main/runtime/dictionary-runtime-main-deps.ts`
+- `src/main/runtime/field-grouping-overlay-main-deps.ts`
+- `src/main/runtime/jellyfin-client-info.ts`
+- `src/main/runtime/jellyfin-playback-launch.ts`
+- `src/main/runtime/mpv-client-runtime-service.ts`
+- `src/main/runtime/mpv-jellyfin-defaults.ts`
+- `src/main/runtime/mpv-main-event-bindings.ts`
+- `src/main/runtime/mpv-osd-log-main-deps.ts`
+- `src/main/runtime/overlay-runtime-bootstrap-handlers.ts`
+- `src/main/runtime/overlay-runtime-options-main-deps.ts`
+- `src/main/runtime/overlay-runtime-options.ts`
+- `src/main/runtime/overlay-visibility-runtime-main-deps.ts`
+- `src/main/runtime/startup-config-main-deps.ts`
+- `src/main/runtime/subtitle-tokenization-main-deps.ts`
+- `src/main/runtime/tray-runtime-handlers.ts`
+- `src/main/runtime/cli-command-context-factory.test.ts`
+- `src/main/runtime/composers/app-ready-composer.test.ts`
+- `src/main/runtime/composers/mpv-runtime-composer.test.ts`
+- `src/main/runtime/overlay-runtime-bootstrap-handlers.test.ts`
+- `src/main/runtime/overlay-runtime-options-main-deps.test.ts`
+- `src/main/runtime/cli-command-context-main-deps.test.ts`
+- `src/main/runtime/subtitle-tokenization-main-deps.test.ts`
+- `src/main/runtime/jellyfin-playback-launch-main-deps.test.ts`
+- `src/main/runtime/jellyfin-playback-launch.test.ts`
+- `src/main/runtime/mpv-jellyfin-defaults-main-deps.test.ts`
+- `src/main/runtime/mpv-jellyfin-defaults.test.ts`
+- `src/main/runtime/field-grouping-overlay-main-deps.test.ts`
+- `src/main/runtime/mpv-osd-log-main-deps.test.ts`
+- `src/main/runtime/overlay-visibility-runtime-main-deps.test.ts`
+- `src/main/runtime/startup-config-main-deps.test.ts`
+- `backlog/tasks/task-105 - Eliminate-unsafe-non-test-runtime-casts-in-main-boundaries.md`
+
+## Assumptions
+
+- TASK-105 scope excludes test-only casts and non-main-runtime paths.
+- Existing compile/test lanes are authoritative for regression detection.
+
+## Phase Log
+
+- `2026-02-22T19:47:35Z` Session started; loaded backlog workflow overview, subagent coordination docs, and TASK-105 details.
+- `2026-02-22T19:52:30Z` Wrote plan at `docs/plans/2026-02-22-task-105-unsafe-runtime-casts.md`, set TASK-105 In Progress, and executed runtime cast-elimination with parallel subagents.
+- `2026-02-22T21:10:04Z` Completed cast elimination in non-test target scope; follow-up type harmonization done for tray/bootstrap/test contracts.
+- `2026-02-22T21:55:38Z` Verification complete: cast scan after=0, targeted runtime tests green, `test:core:src` green; temporarily blocked on unrelated `note-update-workflow.test.ts` TS errors during `bun run build`.
+- `2026-02-22T21:56:30Z` Re-ran `bun run build` after concurrent compile-fix; build passes. TASK-105 finalized Done in Backlog with AC/DoD evidence.
+
+## Next Step
+
+- TASK-105 complete. Optional next step: stage/commit focused TASK-105 diff once user requests commit.