refactor(frontend): decompose Step2/Step3/Step4 wizard components (each >700 LOC)

[arn0ld87]

Follow-up to audit master issue #571.

Problem

Four Vue components are over 700 LOC and pack too many responsibilities:

• frontend/src/components/Step2EnvSetup.vue — 940 LOC
• frontend/src/components/Step3Simulation.vue — 1124 LOC
• frontend/src/components/Step4Report.vue — 1010 LOC
• frontend/src/views/SettingsView.vue — 847 LOC

Hard to test, review, and refactor. The pattern of extracting sub-components is already established (ReportOutlinePanel at Step4Report.vue:19).

Fix policy

Per file, identify 2–4 cohesive sub-units and extract as child components or composables. Examples:

• Step3Simulation.vue → extract <SimulationProgressPanel>, <PersonaActionFeed>, <TimelineControls>.
• Step4Report.vue → extract <ReportExportControls>, <EvidenceBindingsPane>, <PersonaQuoteList> (some may already exist; ride existing patterns).
• SettingsView.vue → split provider settings, workspace defaults, advanced toggles into tabs.

This is iterative — don't try all four in one PR. Recommend filing this as four sub-issues (one per component) once the approach is locked.

Acceptance criteria

• No component over 600 LOC after the split.
• All existing Vitest specs still pass; new spec per extracted child component.
• No visual regression in workspace (manual e2e: Step1 → Step5 happy path).
• Pinia store usage unchanged (no state-shape drift).

Validation

cd frontend && npm run check
cd frontend && npm test -- --run Step
# manual: npm run dev → walk Step1 → Step5

Risk

Medium. Pure decomposition but touches the user-facing wizard; recommend agora-frontend-worker on Sonnet, one component per PR.

Related

• Master: Jules: Comprehensive repository audit and improvement plan #571

[google-labs-jules]

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