Restyle comment inputs with BB tokens

[brsbl]

Summary

• Keeps the existing Moss-like comment input structure and interactions while applying BB input, ring, background, recessed, muted, and destructive tokens.
• Covers empty, focused, populated, submitting, validation-error, server-error, and disabled states without changing comment behavior.
• Keeps the submit button exactly unchanged: same markup, icons, copy, dimensions, placement, hover/disabled appearance, keyboard shortcut, and submission behavior.

Visual evidence

Both revisions use the same real BB dev app, thread selection, fixture text, 1440x900 viewport, and window bounds.

Before — browser-native textarea focus	After — BB focus treatment on the whole input

Empty + disabled	Populated	Submitting

Validation error	Server error with draft retained

Validation

• npm run check --workspace=bb-plugin-timeline-comments — 7 files, 66 tests
• npm run test:browser --workspace=bb-plugin-timeline-comments
• Browser fixture verifies compact/multiline transitions, empty/disabled, focus, populated, validation error, submitting, failed-submit recovery, editing, portals, and responsive re-entry
• git diff --check

BB-Thread-ID: thr_bwikffmsvp