Mint RC observer link and terminal QR after host start

[AetherAI3]

Summary

After an RC host is attached and its opening events have broker receipts, mint a one-time, owner-scoped observe grant and print its expiry, canonical browser link and a terminal QR when the width permits. aether rc link retries the invitation without restarting the session. A failed mint leaves the active host state intact and reports the retry command.

The link carries the short-lived grant in a URL fragment. The matching Cloud web change is AETHER-CLOUD #1909 (merged); its /rc page strips the fragment and redeems with an authenticated POST, including across owner sign-in in the same tab.

The QR renderer is a reviewed, source-controlled workspace package with upstream Apache-2.0 and MIT notices. Its runtime files are bundled and checked by the production package verifier; examples and upstream tests are excluded from the published package.

Verification

• Full local Agent suite: 2,941 tests; 2,902 passed, 39 skipped, 0 failed (486.98 seconds).
• TypeScript build passed.
• 76 focused RC, release-truth and packaging tests passed, including a real npm pack install and launch of the CLI.
• Generated command docs check and diff whitespace check passed.
• GitHub Actions jobs failed at startup before executing steps; hosted build was neutral. The local full suite is the code test evidence for this PR.

Scope

This addresses the observer-link prerequisite in Aether Agent #224 for Predator #107. It does not provide browser frames through Aether RC, Agent Browser controller authority, or a live deployed phone-view proof. Predator #107 remains open until those are demonstrated.