Zed nightly: agent_servers: Integrate inactive v2 receipt submissions (#65653)

Real adapter-created threads now select receipt mode during
construction, send acceptance requests, correlate user-message echoes
and consume reported activity without treating RPC completion as turn
completion.

• Use one owner-aware ReceiptSessionSubmissions::submit operation,
  replacing the overlapping prompt/submit entry points. The v2 adapter
  pins publication to the submitting entity; native and stub transports
  use the same carrier with ordinary, unacknowledged responses.
• Select the capability before registration completes, rather than
  permanently leaving new threads in legacy mode because their map entry
  does not exist yet.
• Validate baseline versus advertised image/audio/embedded-context
  prompt content before publication, including calls through the low-level
  prompt helper. Keep source content unchanged.
• Separate receipt delivery from application with ReceiptSubmission.
  The shared tracker commits success or failure before acknowledging; SDK
  dispatch then finalizes request-scoped input before releasing later
  traffic. This replaces the scheduler/no-yield contract with an explicit
  handshake and reuses the existing submission state machine.
• Distinguish callback/transport loss from wire rejection and reuse
  shared disconnect settlement. No second submission state machine,
  automatic resend, synthetic Idle or LegacyCompleted response.

Release Notes:

• N/A