fix(desktop): seed new sessions from Settings profile default model

[fkhb90]

What

Clicking 「新工作階段」 (New Session) used to inherit the composer
model/provider from the most recently focused conversation, so a session
that was opened on minimax-m3 would silently drag the next new session
off the user's openai-codex / gpt-5.5 profile default. Only an explicit
picker choice or restarting the app reset it. The Settings panel's chosen
default was effectively decorative in the common flow.

Why now

The composer model is sticky UI state by design (preserves the user's
deliberate picker choice across send/receive), but 'New Session' is the
one path that should NOT inherit a focused conversation's last-known
model. This PR fixes that path only and leaves explicit picker choices
sticky.

Reproduction (before the fix)

1. Open Hermes Desktop with the default profile set to e.g. openai-codex / gpt-5.5
2. Open a different conversation, switch its model to minimax-m3
3. Return to the composer and click 新工作階段
4. Expected: new draft shows openai-codex / gpt-5.5
5. Actual: new draft shows minimax-m3 (sticky from the previously focused session). The Settings default is ignored.

Reproduction (after the fix)

Steps 1–5, but step 5 now matches the expectation. A deliberate picker
choice in step 2 is preserved across subsequent send/receive (sticky
behavior unchanged); only the New Session path now seeds from the
profile default.

Changes

File	Role
store/session.ts	Add $freshDraftUsesProfileDefault atom + setter. True only for the visible New Session draft path.
use-session-actions/index.ts	In startFreshSessionDraft, set the flag, seed $currentModel/$currentProvider from the profile default, and clear the localStorage override keys.
use-session-state-cache.ts	When the flag is on and no session is active, ignore stale runtime metadata that an old focused session may still emit during the React-effect gap. Without this guard, the old session's session.info could overwrite the freshly seeded profile default.
desktop-controller.tsx	Pass forceFromProfileDefault=true to refreshCurrentModel on the visible New Session path.
use-model-controls.ts	Clear the override on the initial draft when no focused session is active, so the composer/profile-default split is consistent across both entry points.
use-session-actions.test.tsx	Cover the new flag handling and the pre-send localStorage reset, including the stale-runtime-metadata guard.

Verification

• npm run typecheck — exit 0
• npm run lint — exit 0
• npm run test:ui — passing (including the updated tests in this PR)
• End-to-end on Windows: npm run pack into release/win-unpacked, restart
  Hermes Desktop, open a minimax-m3 session, return to the composer,
  click 新工作階段 → new draft shows openai-codex / gpt-5.5 and stays
  there across subsequent new-session clicks until the picker is used.

Risk

Low. The change is confined to the New Session entry path. Existing
sticky-composer behavior (user makes a deliberate picker choice) is
preserved; only the New Session initial seed changes. A deliberately
chosen model is sticky; an inherited one is no longer.

[alt-glitch]

This was generated by AI during triage.

Competing fix for the same Desktop new-session model-inheritance bug as #55630 (filed minutes earlier, Fixes #54906). Same goal, different mechanism: #55630 uses a $draftModelOverridePending flag on session.create; this PR adds a $freshDraftUsesProfileDefault atom and additionally ignores stale runtime metadata in use-session-state-cache.ts. Related, not a duplicate — a maintainer should pick one. Same area as feature #50013 and fix PRs #48946/#50198.

[tonydwb]

Code Review Summary

Verdict: LGTM

Fixes desktop model seeding to use Settings profile default model for new sessions instead of stale composer/session overrides.

✅ Looks Good

• Clean implementation: refreshCurrentModel(true) forces reseed from profile default
• Good test coverage with new tests for fresh draft behavior
• Well-scoped fix for desktop model selection
• Follows existing pattern for profile swaps

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Reviewed by Hermes Agent