fix: clarify signaling token debug semantics in project CLI

[littleDogWang]

Summary

project doctor treated the Console signaling Token debugging switch as token issuance capability. When the switch was off, it emitted TOKEN_CAPABILITY_DISABLED and returned exit code 2 even for an otherwise ready project. The CLI now names that status signalingTokenDebugEnabled in project show and no longer uses the debug switch as a readiness gate. The BFF wire field remains tokenEnabled for compatibility with the existing service.

Type of change

• Bug fix (non-breaking)
• Behavior change to an existing command (potentially user-visible)
• Breaking change (CLI flag, exit code, JSON shape, or error.code rename/removal)

Public-contract impact

• Adds or changes a JSON envelope shape: project show --json returns data.signalingTokenDebugEnabled instead of data.tokenEnabled. The boolean value is unchanged (true corresponds to need_token=0).
• Renames or removes an error.code: the misleading TOKEN_CAPABILITY_DISABLED warning is removed.
• Changes an exit code for an existing command: when that warning was the only issue, project doctor now exits 0 instead of 2.

Before: project show --json included "tokenEnabled": false; project doctor --json returned "status":"warning", "ok":false, and exit code 2 for the same project.

After: project show --json includes "signalingTokenDebugEnabled": false; project doctor --json returns "status":"healthy", "ok":true, and exit code 0 when no other issue exists. Pretty project show labels the value Signaling Token Debug.

Test plan

• go test ./... passed in an isolated temporary checkout. The local home directory has a .agora/project.json binding that otherwise contaminates existing integration tests.
• make lint passed its gofmt, error-code coverage, and generated-doc checks in the isolated checkout. golangci-lint was not installed, so its optional check did not run.
• JSON and pretty project show behavior are covered by TestCLIProjectUseShowFeatureAndDoctorHappyPath.
• Both debug-switch states are covered by TestBuildProjectDoctorIgnoresSignalingTokenDebug.

Documentation

• CHANGELOG.md updated.
• docs/automation.md updated with the field migration.
• docs/error-codes.md updated to remove the warning and correct the App ID check description.

Security checklist

• No credentials, App Certificates, tokens, or PII added to fixtures, logs, or test output.
• No new outbound network call, user-home file write, or unsafe import.