fix(channels): support display cards (send_card) in Chat SDK bridge

[glifocat]

Type of Change

• Fix - bug fix or security fix to source code

Description

send_card (the MCP tool exposed by container/agent-runner/src/mcp-tools/interactive.ts) was a silent no-op on every Chat SDK channel because chat-sdk-bridge.ts:deliver() had no branch for content.type === 'card'. The payload fell through to the text fallback, where text was undefined and the function returned without calling the adapter. delivery.ts then marked the message delivered with platformMsgId=undefined and the user saw nothing.

This PR adds the missing branch, mirroring the structure of the existing ask_question branch.

How it works

When a chat-sdk outbound row has content.type === 'card':

• Build a Card from card.title, card.description, and card.children (string or { text } shapes both supported)
• For card.actions, render only entries with a url as LinkButtons inside an Actions row. Non-URL actions are dropped because send_card is fire-and-forget per its tool docstring ("renders a structured card and returns immediately — it does not pause your turn or collect a response"); a callback button would have nowhere to land
• Empty cards (no title, no body) are dropped with a warn log instead of posting a blank message
• Fallback text falls through content.fallbackText → card.description → card.title → empty

How it was tested

• pnpm exec vitest run src/channels/chat-sdk-bridge.test.ts → 12/12 passing (5 new + 7 existing)
• pnpm run typecheck → clean
• Manually reproduced on Discord and Telegram with a running install: cards now render; notifications still work

Backward compatibility

No risk. Pre-fix card payloads in existing outbound DBs were already marked delivered (the bridge returned undefined, which delivery.ts treats as success). They will not be re-delivered after the fix.

Scope

Affects every Chat SDK adapter that goes through the bridge: Discord, Telegram, Slack, Teams, GChat, GitHub, Linear, WhatsApp Cloud, iMessage, Matrix, Webex, Resend.

Closes #2263

[glifocat]

Format check now passes after a57bb8f. The remaining CI failure is the same unrelated pre-existing flake in src/host-sweep.test.ts (resetStuckProcessingRows — orphan claim cleanup, both cases) — reproduces on a clean checkout of upstream main at 1404f7f with pnpm exec vitest run src/host-sweep.test.ts → 2 failed | 12 passed. The fix is in flight as #2209 ("fix(host-sweep): orphan-claim delete missed in tests (regression from #2183)").

This PR's own tests pass: pnpm exec vitest run src/channels/chat-sdk-bridge.test.ts → 12 passed (12), including 5 new cases covering the card branch.