fix(models): restore sticky new-thread selections#9164

Note

Medium Risk Touches orchestration event semantics, a data migration on existing SQLite stores, and what model/options are sent to providers—behavior changes for new threads and legacy project records, though explicit overrides are preserved.

Overview Fixes sticky model selection by stopping automatic project defaults from overriding the app-wide “last used” model and by not persisting catalog option defaults as if the user chose them.

Project defaults are now explicit only: project.create always records defaultModelSelection: null (older clients may still send the field; the server ignores it). Web command-palette and CLI project add, plus auto-bootstrap startup, no longer attach a resolved model to new projects; welcome bootstrap still seeds the first thread via getAutoBootstrapThreadModelSelection. Migration 044 clears projection and project.created payloads for create-time seeds when no later project.meta-updated set a default, while keeping user-configured project defaults.

Provider model options use buildExplicitProviderOptionSelectionsFromDescriptors on web, mobile, and shared code: UI can show descriptor defaults, but dispatch and stored selections include only options the user picked. User docs describe remembered selection vs project override and explicit options.

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Note

Fix sticky model selections by dispatching only explicit options and clearing inferred project defaults

• Adds buildExplicitProviderOptionSelectionsFromDescriptors in model.ts to return only explicitly selected option IDs, replacing descriptor-default materialization across mobile, web, and server dispatch paths
• Server project.create decider now always writes null for the default model selection in project.created events; the command field is retained for compatibility but ignored
• Migration 044 in 044_ClearAutomaticProjectModelDefaults.ts clears inferred create-time model defaults from project projections and rewrites matching project.created event payloads to null, preserving streams with a later explicit metadata update
• Auto-bootstrap welcome-thread creation no longer attaches a model default to the project; the welcome thread receives the canonical selection directly
• Behavioral Change: ProjectCreateCommand default model field is now ignored by the server; clients must use project metadata updates to set explicit defaults. Existing projects with inferred defaults from create-time will have those defaults cleared by migration 044

^{Macroscope summarized 649672a.}