feat(server): Claude Sonnet 5.5 and Codex 0.156 rollback

[TheDarkPhantom]

Problem

• Anthropic shipped Claude Sonnet 5.5 (claude-sonnet-5-5, Claude Code CLI 2.1.284). Upstream added it in Add Claude Sonnet 5.5 to the model manifest pingdotgg/t3code#14152 via a model manifest the fork doesn't have, so the picker can't offer it.
• Codex 0.156 removed thread/rollback, so undoing turns in Codex threads fails there.

Fix

Claude Sonnet 5.5 (mirrors the fork's Opus 5.5 wiring, 2876a87)

• New claude-sonnet-5-5 entry in ClaudeProvider.ts with upstream's sonnet-5 profile: effort low..max plus ultrathink, 200k default with 1M opt-in, no fast mode.
• Gated on CLI 2.1.284. Its upgrade nudge now sits at the top of the ladder, above Opus 5.5 (2.1.280).
• Extra High effort stays Extra High (added to the xhigh list in normalizeClaudeCliEffort).
• Aliases sonnet-5.5, claude-sonnet-5.5, claude-sonnet-5-5. Bare sonnet and the default model stay on Sonnet 5, as upstream.
• Marked New in the picker next to Opus 5.5.

Codex rollback (logic ported from pingdotgg#13481 and the helpers from pingdotgg#11338; no Effect upgrade, no protocol regeneration)

• rollbackCodexThread reads the thread's historyMode. For paginated threads (the Codex 0.156 case) it lists turns with thread/turns/list and calls thread/revert { beforeTurnId } at the first turn it drops.
• Older Codex compatibility: the fork's pinned protocol has no historyMode, thread/turns/list, or thread/revert, so older Codex versions do still exist in the wild. Threads that report no historyMode or legacy keep the count-based thread/rollback. This routes on the history mode Codex reports instead of trying revert and falling back on method-not-found. The reason: on Codex versions that have both methods, thread/revert rejects legacy threads with a normal request error, not method-not-found, so a try-and-fall-back approach would break those threads. Legacy threads on 0.156 can't be rolled back at all (upstream has the same limit).
• readThread now pages through thread/turns/list for paginated threads too.
• The new methods go through client.raw.request, since the generated protocol lacks them.
• The adapter's rollback error now names the Codex request that actually failed, where it used to always say thread/rollback.

Verification

• vp test run on CodexSessionRuntime, ClaudeAdapter, ProviderRegistry, CodexAdapter, shared model, and parseChangelog tests: every new test passes. These include paginated revert for 1/2/3/5 turns, the no-turns case, cursor cycles, the legacy rollback path, a surfaced rollback rejection, Sonnet 5.5 gating at 2.1.284/2.1.283, and xhigh kept.
• ProviderRegistry has 1 to 3 failures that change from run to run, all in OpenCode and Codex binaryPath re-probe tests. They're unrelated to this change, and the file is already known to be flaky.
• tsgo --noEmit passes for apps/server, apps/web, packages/contracts, and packages/shared.
• vp lint and vp fmt are clean on changed files. vp run check:avicode passes.

🤖 Generated with Claude Code