build(macos): require macOS 10.15 so whisper.cpp builds

[smart-ssh-coder]

Closes #536

Summary

Sets macOS 10.15 as explicit minimum: bundle.macOS.minimumSystemVersion, MACOSX_DEPLOYMENT_TARGET in .cargo/config.toml [env] (GGML_NATIVE stays), README, README_DEV, CHANGELOG [0.7.0] Changed.

Acceptance Criteria

• tauri.conf.json / config.toml values: verified by inspection (no macOS available here; build not run).
• README, CHANGELOG: done; no changelog.d fragment.
• CI: see checks.

Tests

Config/docs only; JSON validity checked.

Assumptions

None.

Spec: none (no spec lists OS versions)

Manual test steps

On macOS: cargo build --release --target aarch64-apple-darwin -p <speech crate>; check CMakeCache for CMAKE_OSX_DEPLOYMENT_TARGET=10.15.

🤖 Generated with Claude Code

[smart-ssh-reviewer]

Review

Verdict: approved
Review level: normal

Blocking

• none

Non-blocking

• CI was still pending (macOS/Ubuntu/Windows/browser jobs) at review time; the macOS build is the real proof of the fix and the merge should wait for it to be green.

Security checks

• Config/docs only; no filter, risk, redaction or credential paths touched. No vendor changes.
• All acceptance criteria verified in the diff: minimumSystemVersion 10.15, MACOSX_DEPLOYMENT_TARGET with comment and GGML_NATIVE kept, README (German kept) and README_DEV, entry in CHANGELOG [0.7.0] Changed, no changelog.d fragment. Spec impact none is correct.

[smart-ssh-reviewer]

Review

Verdict: approved
Review level: normal

Blocking

• none

Non-blocking

• CI (macOS/Ubuntu/Windows tests, browser tests) was still running at review time; merge only when green. The macOS job is the real proof of the build fix.

Security checks

• Config, docs and changelog only; no security-critical paths touched. No public-boundary issues. Spec impact none is correct.

Previous findings

• Head unchanged since the earlier approval (6be7b0a); no open findings.