Fix Rust AppHost run-session notification routing

[Adam Ratzman (adamint)]

Description

Rust AppHosts launched through CodeLLDB or cppvsdbg could send an empty run-session ID to DCP before the real Rust resource started. DCP rejected that notification and recycled the shared connection, which could leave the resource at PID 0 with no logs or proxy while the adapter-owned process kept running.

This keeps AppHost adapter events on the AppHost lifecycle path instead of reporting them as resource events. It also rejects empty run-session IDs at the extension's DCP boundary so another producer cannot send the same invalid payload.

The Rust NoDebug launch path remains unchanged. We still use the configured adapter to launch the AppHost; we just no longer treat that AppHost child as a DCP resource run.

Validation:

• Extension lint passed.
• Full extension unit suite: 2,754 passing, 5 pending.
• Focused AppHost lifecycle and DCP wire regressions: 2 passing after rebasing onto current main.

Fixes #19750

Checklist

• Is this feature complete?
  • Yes. Ready to ship.
  • No. Follow-up changes expected.
• Are you including unit tests for the changes and scenario tests if relevant?
  • Yes
  • No
• Did you add public API?
  • Yes
    • If yes, did you have an API Review for it?
      • Yes
      • No
    • Did you add <remarks /> and <code /> elements on your triple slash comments?
      • Yes
      • No
  • No
• Does the change make any security assumptions or guarantees?
  • Yes
    • If yes, have you done a threat model and had a security review?
      • Yes
      • No
  • No

[github-actions]

🚀 Dogfood this PR with:

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[Copilot]

Copilot review overview

Review tier: Balanced
Findings: None

What changed in this PR

Prevents Rust AppHost adapter lifecycle events from corrupting DCP run sessions.

Changes:

• Separates AppHost lifecycle events from resource notifications.
• Rejects empty run-session IDs at the DCP boundary.
• Adds focused regression tests.

File	Description
extension/​src/​debugger/​adapterTracker.ts	Suppresses DCP lifecycle notifications for AppHosts.
extension/​src/​dcp/​AspireDcpServer.ts	Drops and logs notifications with empty session IDs.
extension/​src/​test/​adapterTracker.test.ts	Tests AppHost lifecycle routing.
extension/​src/​test/​aspireDcpServer.test.ts	Tests empty-ID rejection before delivery.

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[Ella Hathaway (ellahathaway)]

I reviewed the AppHost-versus-resource adapter routing, DCP run-session lifecycle and wire-delivery paths, Rust adapter behavior, shutdown/restart/telemetry ownership, and focused regression coverage.

I found no correctness issues. I left one nonblocking maintainability note about removing a delivery method made unreachable by this change.