feat(desktop): add removable agent audience chips

[BrianInAz]

Summary

• Replace count-only persistent-agent audience presentation with named, removable Desktop composer chips.
• Remove a recipient from the live draft, hydrated mention token, and persisted thread audience; explicit @mention re-additions promote again only after a successful send.
• Keep manual exclusions composer-local and use identity-safe hydrated labels when duplicate display names are present.

Validation

• cd desktop && pnpm test (3953 passing)
• cd desktop && pnpm typecheck && pnpm check
• cd desktop && pnpm build:e2e
• cd desktop && pnpm exec playwright test persistent-agent-audience.spec.ts --project=smoke --reporter=line (11 passing)

Screenshots are posted in a follow-up comment.

[gemini-code-assist]

Caution

The consumer version of Gemini Code Assist on GitHub has been sunset. All code review activity has officially ceased.

[BrianInAz]

Named persistent audience chips

The effective agent audience is rendered as named, accessible removable chips above the composer.

Dark theme

The same chip editor remains legible in the dark theme.

Removed audience at narrow width

Removing Morgarita leaves only Vogue in the hydrated draft and keeps the composer within the narrow layout.

[gemini-code-assist]

Caution

The consumer version of Gemini Code Assist on GitHub has been sunset. All code review activity has officially ceased.

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