fix: harden incremental validation defaults

[ElbertePlinio]

Summary

• enable local incremental transcription by default while keeping partial segment cleanup opt-in
• keep successful raw paste as a neutral status when cleanup is unavailable, instead of surfacing the cleanup fallback as a red error
• stabilize Settings callbacks so switching views during active recording does not churn parent state on every live update

Issue #14 slice

Refs #14. This is the PR5/manual validation default-decision slice after the user validated incremental performance. Remaining release work is the normal release/tag flow.

LauraGPT's note about a thin segment transcriber interface is already covered by the existing Rust SegmentTranscriber abstraction in the incremental core; no new abstraction is needed in this patch.

Validation

• model-orchestration read-only review: no concrete correctness findings
• bun run check
• cargo test --workspace --locked --all-targets
• bun run test
• bun run test:coverage
• git diff --check
• rustfmt --edition 2024 src/config.rs src-tauri/src/engine.rs

Not tested

• cargo fmt --all --check cannot run here because this stable toolchain is missing cargo-fmt.
• Live manual validation after this rebase onto the new studio chrome main.

[ElbertePlinio]

@codex review

[chatgpt-codex-connector]

Codex Review: Didn't find any major issues. Another round soon, please!

Reviewed commit: 70f67f2578

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[ElbertePlinio]

@codex review

[chatgpt-codex-connector]

Codex Review: Didn't find any major issues. Hooray!

Reviewed commit: 22e10f5572

ℹ️ About Codex in GitHub

Your team has set up Codex to review pull requests in this repo. Reviews are triggered when you

• Open a pull request for review
• Mark a draft as ready
• Comment "@codex review".

If Codex has suggestions, it will comment; otherwise it will react with 👍.

Codex can also answer questions or update the PR. Try commenting "@codex address that feedback".