PR #23766 real-environment server verification

Revisions
  github/main: 6575ce32508bd7908444241f3719aa33aaf77f90
  PR head:     715c19dee2cee78e065e6b0bdf2b103e7a30158d

Path exercised
  Isolated development server -> real Codex app-server process.
  User-facing web client and server CLI; gpt-6.1-sol through local proxy.
  No mocks, fixtures, demo data, or injected notification frames.

Before: github/main, real Codex 0.120.0
  initialize response independently identifies app-server version 0.120.0.
  Incoming decoded native notification counts:
    thread/started: 5
    mcpServer/startupStatus/updated: 20
  Schema decoding summary:
    thread/started: 5 failures
    issueKinds: Composite, Pointer, MissingKey
    issueCount: 5; maximumPathDepth: 2
    mcpServer/startupStatus/updated: 20 successes
  Targeted "Dropped a Codex App Server notification that failed to decode" warnings: 0.
  Original missing diagnostic reproduced with genuine provider notifications.

After: exact PR head, real Codex 0.120.0
  initialize response independently identifies app-server version 0.120.0.
  Incoming decoded native notification counts:
    thread/started: 5
    mcpServer/startupStatus/updated: 20
  Targeted warning count: 1, despite five repeated rejected notifications.
  Captured server warning:
    WARN: Dropped a Codex App Server notification that failed to decode
      operation: decode-notification-payload
      method: thread/started
      issueCount: 5
      issueKinds: [ Composite, Pointer, MissingKey ]
      maximumPathDepth: 2
  The warning block contains no provider payload, prompt text, or error cause.
  Later native startup notifications remain observable.

Nearby behavior
  Real Codex 0.164.0 completed a gpt-6.1-sol turn through the PR web client.
  Normal Codex 0.164.0 produced no live notification schema decode failures.
  Additional real normal-CLI turns completed through the server CLI.
  Existing focused Codex client checks: 3 passed through Blacksmith.

Limits
  Codex 0.120.0 also has a thread/start response schema mismatch, so its
  agent turn fails with: Invalid payload for method 'thread/start' during 'decode-payload'.
  This PR adds diagnostics; it does not repair incompatible provider schemas.
  Old-CLI turn completion is not claimed. Normal-CLI turns cover successful dispatch.
  Changing a provider binary setting did not restart an existing shared process;
  verification restarted that provider and confirmed the real initialized version.
  Native desktop/mobile clients and other operating systems were not exercised.

Evidence handling
  Summary transcribed from native protocol logs, main decoding summary, server
  output, and CLI outcomes. Raw payloads, credentials, IDs, and private paths omitted.