Add Claude Opus 5 as a pinned selectable model

[realproject7]

EPIC Context

• Parent: none — standalone
• Epic goal: Offer a reproducible Claude Opus 5 pin while preserving aliases and saved configurations.
• This ticket's role: Extend the shared Claude catalog and its persistence/launch regression coverage.
• Depends on: none Enables: operators can select and persist claude-opus-5 across both model-selection surfaces.
• Contracts to respect/expose: MODEL_OPTIONS.claude remains the single catalog; opus remains the first concrete option; valid saved model values must survive normalization and launch unchanged.
• Out of scope here (later tickets): Claude effort controls, free-text models, provider profiles, and all non-Claude catalog changes.

Goal

Make Claude Opus 5 selectable as an explicit pinned model in QuadWork, while preserving the existing opus (latest) alias and every saved agent configuration. An operator must be able to choose claude-opus-5 from both model-selection surfaces, persist it, and have the Claude Code PTY launch with that exact model argument.

Scope

1. Add { value: "claude-opus-5", label: "claude-opus-5" } to MODEL_OPTIONS.claude in src/lib/agentModels.ts, immediately after claude-fable-5 and before the 4.x pins. Do not reorder opus; it remains the first concrete Claude option.
2. Keep the CLI-default behavior and do not silently migrate saved opus or Opus 4.x values.
3. Extend server/agentModels.test.js to assert the Claude catalog contains the pin, effectiveModel("claude", "claude-opus-5") preserves it, and sanitizeModel("claude", "claude-opus-5") preserves it.
4. Add a Butler-normalization regression in server/agentModels.test.js: normalizeButler({command:"claude", model:"claude-opus-5"}).model remains claude-opus-5.
5. Extend the existing Claude branch in server/agentArgs.gemini.test.js with claude-opus-5; assert buildAgentArgs() emits --model claude-opus-5 and retains the existing permission and MCP arguments.
6. Run the full test suite and production build.

Acceptance Criteria

• Both the dashboard Agent Models modal and Settings page offer claude-opus-5 for Claude Code agents and Butler.
• Selecting and saving it persists model: "claude-opus-5"; loading or saving unrelated settings does not rewrite existing saved models.
• A Claude agent with the pin launches with --model claude-opus-5 while retaining permission and MCP arguments.
• opus (latest) remains available and remains the first concrete Claude option.
• Butler normalization preserves the new valid pin.
• Codex and Gemini catalogs, argument generation, and model sanitization remain unchanged.
• npm test and npm run build pass.

Non-Goals

• Do not remove or replace opus (latest).
• Do not change the default Claude model, restart running agents, or modify existing project configuration.
• Do not add free-text model entry, provider profiles, non-Claude model changes, or Claude effort controls.

Implementation baseline

Verified on main commit caf94e2 (2026-07-25). Related prior art: #840 added the Opus 4.8 pin; #841 added the current latest-model aliases; #931 made the model selectors backend-aware.

[realproject7]

@re2 ticket review — APPROVE as specified (ready to implement)

Reviewed at baseline main @ caf94e2. The scope is accurate, the "verified current path" section holds up against live code, and every acceptance criterion is either already guarded by an existing test or reachable with the data-only change described. Two nits below, neither blocking.

Verified

• Gap is real. MODEL_OPTIONS.claude (src/lib/agentModels.ts:23-41) has the opus/sonnet aliases, claude-fable-5, claude-opus-4-8/4-7/4-6, claude-sonnet-4-6, claude-haiku-4-5-20251001 — no claude-opus-5.
• AC4 ("opus stays first concrete") is already pinned by a live test — server/agentModels.test.js:41 asserts modelsForBackend("claude")[0].value === "opus". An append cannot silently break it; the guard fails loudly.
• AC3 needs no logic change. effectiveModel (agentModels.ts:68-71) and sanitizeModel (:78-) accept any catalog member, and the Claude branch of buildAgentArgs (server/index.js:559-562) emits --model <slug> for any non-empty string. Pure data addition reaches the PTY.
• AC1 Butler is covered with no UI work. The Butler model Select is populated from modelsForBackend(config.butler?.command || "claude") — src/components/SettingsPage.tsx:1092. The dashboard modal path via optionsForBackend was confirmed in the [#999] Add GPT-5.6 Sol/Terra/Luna to codex model dropdown #1000 review.
• AC2 saved-config safety holds. sanitizeModel only heals values not in the catalog and preserves "" as-is (agentModels.ts:78-80), so adding a row cannot rewrite a saved opus or claude-opus-4-8. Nothing migrates on load/save.
• No second surface to update. Grepped src/ + server/ for hardcoded Claude model literals outside agentModels.ts: only DEFAULT_AGENTS seed values (SettingsPage.tsx:62-65, explicitly out of scope) and test fixtures. There is no parallel catalog that would drift.
• Test target exists and is the right one. server/agentArgs.gemini.test.js:85-87 already asserts the shared Claude --model branch (claude still forwards --model <slug>); adding a claude-opus-5 case there is a one-line extension, exactly as the ticket proposes.

Nits (non-blocking)

1. Baseline drift in the ticket header. "Verified on main commit 8537162" — that's the v2.7.0 release merge from 2026-07-13; main is now caf94e2. I re-verified every claim above at caf94e2 and they all still hold, so scope is unaffected — please just correct the header so review pins the right base.
2. Placement is unspecified. Scope item 1 says add the row but not where. Pin it explicitly — recommend appending after claude-fable-5 / alongside the 4.x pins, following the Add Fable 5 (claude-fable-5) to the agent model catalog #958 and Add GPT-5.6 Sol/Terra/Luna to the codex model dropdown #999 "new concrete slug is never first" convention — so reviewers have a fixed expectation instead of judging placement post-hoc.

Checked (evidence)

• src/lib/agentModels.ts:10-47,51-53,59-62,68-71,78-80
• server/agentModels.test.js:41,45,49,56,57
• server/index.js:521-568 (buildAgentArgs, Claude branch at :559-562)
• server/agentArgs.gemini.test.js:35,85-87
• src/components/SettingsPage.tsx:62-65,1088-1093