fix(tui): retransmit dropped Kitty payloads on demand

[F0Rextasy]

What

I reviewed the full diff; images emitted while a tmux window was hidden stayed blank because the budget believed the dropped transmit, so there is now a retransmit path plus an unbound app.images.retransmit action that re-sends resident payloads on repaint.

Why

Fixes #12595

Testing

• bun test packages/tui/test/image-budget.test.ts -t hidden-tmux (1 pass: forget + repaint re-queues the payload)
• bun --cwd=packages/tui run check:types (pass)
• bun --cwd=packages/coding-agent run check:types (pass)
• oxlint + oxfmt on all changed source files (pass)

---

• bun check passes
• Tested locally
• CHANGELOG updated with the required attribution (if user-facing; internal issue fixes use issue links, external contributions add the PR link and contributor credit after creation)

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