feat(web): drive PM provider picker from registry

[aaight]

Summary

Implements the registry-driven PM provider picker for the dashboard wizard.

Card: https://trello.com/c/6a004d924258a2f6ab68dd74

Changes

• Extracted the provider picker into ProviderPicker, rendered from listProviderWizards() so any registered provider appears without editing the picker loop.
• Kept provider switching behavior intact while moving confirmation copy through a label-based message builder using provider definition labels.
• Updated stale registry comments now that the manifest path is mandatory.
• Reworked focused unit coverage to register a non-production stub provider and verify it renders in the picker.

Verification

• npx vitest run --project unit-core tests/unit/web/pm-provider-registry.test.ts tests/unit/web/pm-wizard-generic-renderer.test.ts
• npm run lint:fix
• npm run lint
• npm run typecheck
• cd web && npm run build
• npm test

Notes

• npm run lint passes with existing warning-level complexity/non-null assertion diagnostics outside this change set.

🕵️ codex · gpt-5.5 · run details

[nhopeatall]

LGTM - the provider picker is registry-driven, uses provider definition labels for switch confirmation, and the existing provider switch/reset/save cleanup behavior is preserved. Focused unit tests passed locally, and CI is green.

🕵️ codex · gpt-5.5 · run details