fix(web): describe what Ultracode does in the Reasoning picker

[delltrak]

Closes #6091

Reasoning → Ultracode sits next to Low/Medium/High/Extra High/Max with a bare label. Nothing in the UI says it also turns on standing multi-agent workflow orchestration. Claude Code's own picker spells it out (xhigh + dynamic workflow orchestration).

before	after

ProviderOptionChoice in packages/contracts/src/model.ts already declares an optional description. It just was never plumbed through, so this wires it up and sets one on Ultracode:

• providerSnapshot.ts: buildSelectOptionDescriptor stops dropping description when it maps choices
• TraitsPicker.tsx: renders option.description under the label when there is one
• ClaudeProvider.ts: sets it on ultracode for the three models that offer it (fable-5, opus-5, opus-4-8)

Data-driven rather than a hardcoded ultracode branch in the picker, since #5696 is moving provider-specific logic out of that file. Any provider can annotate any select option now.

Options without a description render exactly as before. No contract change, nothing to migrate.

The description is capped at max-w-56 and wraps, so the menu settles around 250px instead of growing with the text. Menus whose options carry no description keep their current width.

Renaming the label would have been a smaller diff but a worse result. TraitsPicker truncates choice labels, and mobile's compact settings pill reuses the same option.label, so Opus 5 · Ultracode (multi-agent workflows) · Full would land on the one surface that already hides this option on purpose.

#5696 touches ClaudeProvider.ts and TraitsPicker.tsx too. Whichever lands second needs a rebase.

Testing

• vp fmt and vp lint: clean
• typecheck on t3, @t3tools/web, @t3tools/contracts: passes
• vp run --filter @t3tools/web test: 2161 passed across 234 files
• vp run --filter t3 test: 2371 passed, 7 skipped

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[macroscopeapp]

Approvability

Verdict: Approved c60cd35

This PR adds descriptive text to the 'Ultracode' option in the Reasoning picker UI. The changes are purely additive - adding an optional description field to existing data structures and rendering it in the UI. No runtime logic changes beyond displaying text.

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Dismissing prior approval to re-evaluate c60cd35