fix(desktop): read live DOM text for Ctrl+Enter steer to avoid stale-state race

[liuhao1024]

What does this PR do?

Fixes a race condition where Ctrl+Enter / Cmd+Enter in the Desktop chat composer silently missed steer messages when the user typed and immediately pressed the shortcut. The handler gated on canSteer, which derives from React state (trimmedDraft) that lags the contentEditable DOM by one render.

Related Issue

Fixes #53659

Type of Change

• 🐛 Bug fix (non-breaking change that fixes an issue)

Changes Made

• apps/desktop/src/app/chat/composer/index.tsx: Read live DOM text via composerPlainText(editorRef.current) in the Ctrl+Enter handler instead of relying on canSteer (React-state-derived). Sync draftRef.current before calling steerDraft() so the function reads the just-typed text. Remove the canSteer gate from steerDraft() — the Ctrl+Enter handler already validates conditions using live DOM, and the Steer button visibility is separately gated on canSteer via ComposerControls props.
• apps/desktop/src/app/chat/composer/ctrl-enter-steer-dom-race.test.tsx: Regression test covering the stale-state race (DOM has text, React state is empty), empty-editor no-op, not-busy no-op, and whitespace-only no-op.

How to Test

1. Open Hermes Desktop, start a chat turn that is still busy/running.
2. Focus the composer, type a short steering message, and immediately press Ctrl+Enter (Windows/Linux) or Cmd+Enter (macOS).
3. The steer message should be sent reliably every time, regardless of typing speed.
4. Run npx vitest run --environment jsdom apps/desktop/src/app/chat/composer/ctrl-enter-steer-dom-race.test.tsx — all 5 tests should pass.
5. Run npx vitest run --environment jsdom apps/desktop/src/app/chat/composer/enter-submit-dom-race.test.tsx — existing plain-Enter race tests should still pass (5/5).

Checklist

Code

• I've read the Contributing Guide
• My commit messages follow Conventional Commits (fix(scope):, feat(scope):, etc.)
• I searched for existing PRs to make sure this isn't a duplicate
• My PR contains only changes related to this fix/feature (no unrelated commits)
• I've run npx vitest run --environment jsdom on the affected test files and all tests pass
• I've added tests for my changes (required for bug fixes, strongly encouraged for features)
• I've tested on my platform: macOS

Documentation & Housekeeping

• I've updated relevant documentation (README, docs/, docstrings) — or N/A
• I've updated cli-config.yaml.example if I added/changed config keys — or N/A
• I've updated CONTRIBUTING.md or AGENTS.md if I changed architecture or workflows — or N/A
• I've considered cross-platform impact (Windows, macOS) per the compatibility guide — or N/A
• I've updated tool descriptions/schemas if I changed tool behavior — or N/A

Code Intelligence

• Analyzed: apps/desktop/src/app/chat/composer/index.tsx — handleEditorKeyDown Ctrl+Enter branch + steerDraft callback
• Blast radius: LOW — only affects the Ctrl+Enter steer path in the Desktop composer; the Steer button's visibility is separately gated on canSteer via ComposerControls props
• Related patterns: Desktop] Enter key doesn't send message — must add trailing space #39630 (plain Enter stale-state race fix) — same live-DOM-read pattern applied to Ctrl+Enter

[teknium1]

Thanks for isolating the stale DOM/state race; the current main path still has the underlying defect.

Problems

• This branch changes the old inline steerDraft implementation, but current main extracted it in 773a3703bfc1f8ff2f3aef40d7a565e7f4fe1404. The live shortcut still gates at apps/desktop/src/app/chat/composer/index.tsx:551, and the extracted implementation independently returns on stale canSteer at apps/desktop/src/app/chat/composer/hooks/use-composer-submit.ts:176-179. GitHub currently marks the PR DIRTY, so the fix needs a targeted port to those current paths.
• ctrl-enter-steer-dom-race.test.tsx:16 tests a copied Harness rather than production ChatBar/useComposerSubmit; it cannot prevent a regression in the live implementation. It also lacks coverage for attachment and slash-command exclusions.

Suggested changes

• Port the live-DOM validation and draft-ref synchronization to the current keydown path, and update the extracted steer guard without weakening the text-only/non-slash contract.
• Add coverage through the current production component or submit hook for stale DOM text plus slash and attachment no-op cases.

Automated hermes-sweeper review.

[teknium1]

This Harness duplicates the proposed implementation instead of exercising ChatBar or the extracted useComposerSubmit production path. On current main, the second stale canSteer gate lives in hooks/use-composer-submit.ts:176-179, so this test can pass while the shipped shortcut still fails. Please replace or supplement it with a test through the current component/hook boundary.