models: add Claude Opus 5.5 and make it the bundled Opus executor

[Tryanks]

Claude Opus 5.5 (claude-opus-5-5, released 2026-09-22) joins the
bundled Claude catalog as the current Opus: 1M context with the [1m]
suffix, fast mode, and the API's medium default effort. Opus 5 becomes
legacy and hands the bare opus alias to 5.5. The entry is gated on
Claude Code 2.1.280, the release that added the model.

The t3code manifest tcode mirrors does not list Opus 5.5 yet, so the
bundle is edited in the upstream shape and dated ahead of it. A fetched
manifest older than the bundle by updatedAt is now left unadopted
(while still counting as a fetch for the TTL), the same rule the disk
cache already followed; without it the hourly refresh would have
replaced the bundle with the stale upstream copy.

Orchestrate's built-in Claude executor moves from Opus 5 to Opus 5.5. An
untouched bundled Opus 5 row migrates with it unless the user already
added Opus 5.5; rows with custom guidance or an endpoint profile stay on
Opus 5. Legacy fixed-effort rows on Opus 4.8 or Opus 5 now land on 5.5.

Checks

• cargo fmt --all --check, cargo clippy --workspace --all-targets --locked -- -D warnings, cargo nextest run --workspace --locked (927 passed, 5 skipped)

Notes

• Upstream t3code manifest still lacks Opus 5.5; the bundle is dated 2026-09-23 so the refresh rule keeps it until upstream catches up, after which a verbatim copy can replace it again.
• The model is hidden on Claude Code older than 2.1.280.