cli: --app-info probe + --format json envelope

[cliffhall]

Summary

App-probing and machine-readable output for the CLI:

• --method tools/call --tool-name <t> --app-info — prints one JSON line describing the tool's app posture (hasApp, resourceUri, csp, permissions, …) without invoking the tool; exits 0 when the tool has an app, 2 (no_app) when it doesn't — so a shell pipeline can short-circuit before touching a browser.
• --method tools/list --app-info — one NDJSON line per tool with its _meta.ui posture, over a single connect.
• --format json — a single JSON envelope on stdout (result + appInfo as sibling keys, no banner) for any method.

Reference implementation (PR #1510)

Re-implement informed by these changes at 33fac3f:

• clients/cli/src/cli.ts — collectAppInfo() (uses core extractAppInfo() + resource read), NDJSON loop in tools/list, emitResult() output envelope, OutputFormat type
• clients/cli/tests/app-info.test.ts — exit-2 vs exit-5 distinction, NDJSON emission (+154)
• clients/cli/tests/format-and-args.test.ts — --format json envelope tests

Depends on

• core AppInfo + extractAppInfo()
• CLI exit-code map + error envelopes (NO_APP = 2 via CliExitCodeError)
• mcp_app_demo test-server preset (live fixture for the tests)
• CLI ergonomics issue (same cli.ts lane; land first)

--format json and --app-info are combined here because emitResult() branches on both — splitting them creates an artificial seam.

Notes

• Resource-read failures during the probe should be tolerated and reported in a resourceError field, not thrown.
• Document --app-info, --format json, NDJSON shape, and the exit-2 semantics in clients/cli/README.md.
• Coverage gate ≥90 on all four dimensions.

Part of the PR #1510 decomposition (see tracking issue).