feat(core): add Discord presence service and extract Jellyfin runtime composition

Introduce Discord presence runtime support and continue composition-root decomposition by moving Jellyfin wiring into dedicated composer modules. This keeps main runtime orchestration thinner while preserving behavior and test coverage across config, runtime, and docs updates.

docs/subagents/agents/codex-task104-launcher-config-20260222T194708Z-z9x1.md

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+# Agent: `codex-task104-launcher-config-20260222T194708Z-z9x1`
+
+- alias: `codex-task104-launcher-config`
+- mission: `Execute TASK-104 end-to-end with plan-first workflow and no commit`
+- status: `done`
+- branch: `main`
+- started_at: `2026-02-22T19:47:08Z`
+- heartbeat_minutes: `5`
+
+## Current Work (newest first)
+
+- [2026-02-22T19:47:08Z] intent: load backlog context, write execution plan with writing-plans skill, execute with executing-plans skill, and validate launcher test lanes.
+- [2026-02-22T19:56:26Z] progress: extracted launcher config domain modules (`shared-config-reader`, `youtube-subgen-config`, `jellyfin-config`, `plugin-runtime-config`, `cli-parser-builder`, `args-normalizer`) and reduced `launcher/config.ts` to orchestration facade.
+- [2026-02-22T19:56:26Z] test: `bun test launcher/config-domain-parsers.test.ts launcher/parse-args.test.ts`, `bun run test:launcher`, and `bun run test:fast` all passed.
+- [2026-02-22T19:56:26Z] handoff: TASK-104 finalized Done in Backlog MCP with AC/DoD checks complete and final summary recorded.
+
+## Files Touched
+
+- `docs/subagents/agents/codex-task104-launcher-config-20260222T194708Z-z9x1.md`
+- `docs/subagents/INDEX.md`
+- `docs/subagents/collaboration.md`
+- `docs/plans/2026-02-22-task-104-launcher-config-domain-parsers-cli-builder.md`
+- `launcher/config.ts`
+- `launcher/config/shared-config-reader.ts`
+- `launcher/config/youtube-subgen-config.ts`
+- `launcher/config/jellyfin-config.ts`
+- `launcher/config/plugin-runtime-config.ts`
+- `launcher/config/cli-parser-builder.ts`
+- `launcher/config/args-normalizer.ts`
+- `launcher/config-domain-parsers.test.ts`
+- `launcher/parse-args.test.ts`
+- `launcher/jellyfin.ts`
+- `launcher/types.ts`
+- `package.json`
+
+## Assumptions
+
+- Existing launcher CLI behavior can be preserved with modular extraction plus regression tests.
+
+## Open Questions / Blockers
+
+- none
+
+## Next Step
+
+- await user follow-up (optional: commit, docs wording update, or additional jellyfin session-source hardening).