fix(web): Ollama model validation, credential edit and delete, composer and polling fixes (CL-8464)

[TheGreatAxios]

Summary

• Local Ollama connect now validates the typed model against the base URL's own GET /api/tags, offering a select of pulled models instead of free text.
• Settings → Credentials: delete goes through a visible useMutation over the stock DELETE route, and a credential row can now be edited (name, description, and a base URL / model pair for a local-style credential) through the stock PATCH route.
• Composer: an auto-repeating Enter or Shift+Enter keydown (holding the key) no longer sends multiple messages or inserts multiple newlines from one keystroke.
• Chat and workbench pages: approvals now poll only while an agent is still starting; once live, the existing mailbox SSE invalidation is the only trigger, so one event issues one read instead of an independent interval double-polling the same key.

Changes

• apps/web/src/onboarding/ollama-tags.ts (+test): browser-side fetch/parse of Ollama's native /api/tags.
• apps/web/src/onboarding/provider-connect-step.tsx: model field is now a Select populated from live tags, gated on the model actually being present.
• apps/web/src/settings/credentials-api.ts, credentials-section.tsx, strings.ts: updateCredential (PATCH), an Edit dialog, and create/update/delete converted to useMutation.
• apps/web/src/chat/composer.tsx: event.repeat guard on Enter/Shift+Enter.
• apps/web/src/pages/chat-thread-page.tsx, apps/web/src/pages/workbench-page.tsx: approvals refetchInterval scoped to "an agent is starting"; workbench page's inbox subscription now also invalidates the approvals key.

Testing

• bun run check (typecheck, lint, fmt, full test suite) passes.
• Targeted: bun test src/settings/credentials-api.test.ts, bun test src/onboarding/ollama-tags.test.ts.
• Live verification against a dev stack at localhost:5173 was not completed in this session — no sign-in session/credentials were available to the agent, so items 1, 2, and 4 are unverified beyond the automated tests above.

[linear-code]

CL-8464