feat: add reasoning effort picker to session screen (#47) (#51)

* feat(#49): improve project picker with recents + server projects

- New Session modal now shows:
  - Current project as tappable row (tap to create session immediately)
  - Recent Projects section: list of previously used dirs as tappable rows
  - Server Projects section: projects known to opencode server (from /project API)
  - Manual path input as fallback (unchanged behavior)
- Modal body is now scrollable to handle long lists
- All selection paths call addRecentDirectory to keep recents up to date
- TypeScript clean (pre-existing VariantPicker.tsx error unrelated)

* feat: add reasoning effort (variant) picker to session screen (#47)

- Add VariantPicker bottom sheet component (low/medium/high/auto)
- Add variant state to catalog store, reset on model change
- Pass variant through sendMessage -> sdk.session.prompt()
- Add reasoning chip to toolbar, shown only for models with variants
- Parse model.variants from provider API response in catalog and sdk types

API field: variant in POST /session/:id/prompt_async
Server maps variant -> reasoningEffort via model variant config

* fix(models): preserve reasoning effort across messages

Reset the selected variant only when the provider/model pair actually changes, including catalog reloads and agent-driven model switches.

Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

---------

Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

src/lib/sdk.ts

@@ -418,6 +418,7 @@ export function createClient(config: ClientConfig) {
                 cost?: { input: number; output: number }
                 limit: { context: number; output: number }
                 status?: "alpha" | "beta" | "deprecated" | "active"
+                variants?: Record<string, { reasoningEffort?: string }>
               }
             >
           }>