Defer Hermes task creation until the first message

[ribaricplusplus]

Summary

• make New task open an ephemeral client-side Hermes draft instead of calling the API
• persist the thread only when the first non-empty prompt or branch command is submitted
• isolate draft messages, progress, typing, unread state, and selection from General and persisted tasks
• guard rapid submission, null/error responses, and stale cross-DM persistence
• add focused route tests plus a real compiled-Tauri offline acceptance harness

No backend or schema changes are included.

Acceptance evidence

Authoritative devbox commit: 7c376034e5c92a886ac10d2dfc8857a2d74030f3

Passed

pnpm --filter @thechat/desktop exec vitest run src/routes/dm.test.tsx
6 passed

pnpm --filter @thechat/desktop build
passed

THECHAT_NEW_TASK_E2E_ROOT=/home/dev/.cache/koda-work/86cathhhk-recovery/e2e/run-1 \
  pnpm test:e2e:new-task-client-side
1 compiled Tauri spec passed

The compiled-Tauri run:

• started disposable PostgreSQL, Redis, and API resources
• created a real Hermes DM with zero persisted task rows
• loaded the real compiled desktop app through tauri-driver under Xvfb
• stopped the API, PostgreSQL, and Redis before clicking New task
• confirmed the local draft row and empty composer remained usable
• observed zero browser fetches and zero WebSocket sends from the click
• restarted PostgreSQL without restarting the API and confirmed task rows remained 0 -> 0
• removed all E2E containers and processes after the run

Local review artifacts:

• screenshot: /home/bruno/.cache/koda-work/86cathhhk-recovery/evidence/e2e-run-1/new-task-client-side.png
• machine evidence: /home/bruno/.cache/koda-work/86cathhhk-recovery/evidence/e2e-run-1/ui-evidence.json
• full run log: /home/bruno/.cache/koda-work/86cathhhk-recovery/logs/controller-e2e-run-1.log

Existing baseline failure

The normal desktop unit suite completed with 528 passed, 8 skipped, and one failure:

src/core/compaction.test.ts > isOverflow > accounts for model-specific maxOutputTokens

The exact same compaction assertion fails at untouched base commit 5fc0df1b55c92d7e489b616862c2a173111927b8. This PR does not touch compaction code or tests.

Reviewer commands

pnpm --filter @thechat/desktop exec vitest run src/routes/dm.test.tsx
pnpm --filter @thechat/desktop build
THECHAT_NEW_TASK_E2E_ROOT="$HOME/.cache/thechat-e2e/new-task-review" \
  pnpm test:e2e:new-task-client-side

The E2E command requires Docker, tauri-driver, and xvfb-run. It creates and removes dedicated containers named thechat-new-task-e2e-postgres and thechat-new-task-e2e-redis.