[frontend-perf] Sprint 4 — bundle hygiene: mock out of entry, lazy wizard, drop dead dep

[Santisoutoo]

Part of VforVitorio#875 (Fable-5 frontend perf audit 2026-07-05). Sprint 4 — Bundle hygiene.

• S4.1 perf(bundle): mock API out of the live entry + extract applyChunk [S] — lib/api.ts:23,60 statically composes mockApi (api.mock.ts ~25KB + mock-data.ts ~22KB source) into the entry of live builds; ChatPage.tsx:21 also imports applyChunk from api.mock. AC: env-gated dynamic import of the mock; extract the pure applyChunk (api.mock.ts:624-642) into its own module. (P3)
• S4.2 perf(bundle): lazy-load ModelWizard body behind the gate [S] — ModelWizard (27.7KB source) is eager in the entry (main.tsx:18, ModelWizard.tsx:77-107) but renders only pre-onboarding. AC: lazy-load the wizard body behind the gate boolean (the gate stays eager). Note: TutorialTour-eager is the known perf(app): shrink the entry bundle — lazy routes, vendor chunks, lazy tutorial VforVitorio/LexFlow#712 remaining item — do NOT re-file it here. (P3)
• S4.3 chore(deps): remove dead @xyflow/react [S] — zero imports since [ux] Graph: adopt react-force-graph (2D-canvas + 3D) — replace flat react-flow, supersedes #569 VforVitorio/LexFlow#596 moved to react-force-graph-2d (frontend/package.json:33); not bundled, but install/audit weight. AC: drop the dependency. (P3)

Full detail: memory/fable_frontend_perf_audit_2026-07-05.md.

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Upstream: VforVitorio#879

[Santisoutoo]

Agent loop attempt 1 failed: https://github.com/Santisoutoo/LexFlow/actions/runs/32734919212

[Santisoutoo]

Agent loop infra failure (not an attempt): https://github.com/Santisoutoo/LexFlow/actions/runs/32738838527

[Santisoutoo]

Agent loop attempt 2 failed: https://github.com/Santisoutoo/LexFlow/actions/runs/32749623046