Phase 7g.3: Desktop "Ask…" button

[joaoh82]

Summary

Adds a natural-language → SQL composer to the Tauri desktop app's query editor. Click Ask…, type a question, submit, generated SQL drops into the editor textarea for the user to review + Run themselves.

Editor toolbar:  [ Ask… ]  [ Run ]
                    ↓ click
                 ┌──────────────────────────────────────────────────┐
                 │ Ask                  ⌘↵ submit · Esc close   [×] │
                 │ ┌────────────────────────────────────────────┐  │
                 │ │ How many users are over 30?                │  │
                 │ └────────────────────────────────────────────┘  │
                 │ Generated SQL replaces the editor —     [Generate SQL] │
                 │ review before running.                            │
                 └──────────────────────────────────────────────────┘
                                    ↓ submit
       Editor textarea now contains: SELECT COUNT(*) FROM users WHERE age > 30
       Explanation slot shows: Counts users older than thirty.

Why the API key stays out of the webview

The ask_sql Tauri command runs schema introspection + the LLM HTTP POST entirely in the Rust backend. The webview only ever sees { sql, explanation }. Same security story as Q9's WASM JS-callback shape, achieved here as a natural side effect of how Tauri's command bridge works.

What landed

Layer	Change
sqlrite::ask (engine)	Re-exports the public sqlrite-ask types (AskConfig, AskResponse, AskError, Provider, etc.) so downstream crates that already depend on the engine don't need a separate sqlrite-ask dep just for type names.
desktop/src-tauri/src/main.rs	New ask_sql Tauri command (~30 LOC) — locks Database, reads AskConfig::from_env(), calls sqlrite::ask::ask_with_database, returns { sql, explanation }. Registered in the invoke handler.
desktop/src/App.svelte	New $state vars + handlers (onAskClick, onAskSubmit, onAskKey) + composer markup (~110 LOC). Cmd/Ctrl+Enter submits, Esc closes.
desktop/src/app.css	New styles for .ask-panel, .ask-header, .ask-actions, .ask-explanation, .ask-button, .ask-close using existing CSS variables (~85 LOC).
Docs	docs/desktop.md (commands table + UX bullet), docs/phase-7-plan.md (✅ 7g.3), docs/roadmap.md, README.md (Phase 7 checklist).

Behavior details worth calling out

• Generated SQL is NOT auto-executed. Drops into the editor textarea; user reviews + clicks Run. Mirrors the REPL's confirm-and-run UX.
• Empty SQL response handled. When the model declines (schema can't answer the question), the model's explanation surfaces in the panel instead of erasing the editor or doing nothing silent.
• Errors surface in the existing error slot. Missing API key, network failure, API errors all produce clean messages — no popups or alerts.
• Focus moves back to the editor on success so Cmd/Ctrl+Enter just runs.
• API key sourcing. AskConfig::from_env() reads SQLRITE_LLM_API_KEY from the process env. Tauri inherits the parent shell's env when launched via npm run tauri dev or directly. Production app: users set the env var via system-level config or a future settings panel.

Test plan

• cargo fmt --all -- --check — clean
• cargo check --workspace --all-targets — clean (including sqlrite-desktop)
• cargo check -p sqlrite-engine --no-default-features — minimal lib build still clean (ask feature opt-out works)
• cargo test --workspace --exclude sqlrite-desktop --exclude sqlrite-python --exclude sqlrite-nodejs — 301 / 301 pass
• npm run check (svelte-check) — 0 errors / 0 warnings / 84 files
• CI: rust matrix (linux/macos/windows), python-sdk, nodejs-sdk, go-sdk, wasm-build, desktop-build all green
• Manual smoke: export SQLRITE_LLM_API_KEY=... → cd desktop && npm run tauri dev → New… → CREATE a small users table → click Ask… → "How many users are over 30?" → confirm SQL pastes into editor → Run → verify result

Next up after merge

1. Merge → dispatch release-pr.yml at v0.1.20 → desktop installers (Linux deb / AppImage / rpm + macOS dmg + Windows msi/exe) all carry the Ask… button.
2. 7g.4-7g.6 — Python / Node / Go SDK adapters. Each adds a conn.ask() method on the existing connection class plus an ask_run() convenience wrapper. Parallelizable but small enough to do sequentially.
3. 7g.7 — WASM SDK with the JS-callback shape per Q9 (browser tab does prompt construction in-page; HTTP call goes through caller-supplied JS function so the API key stays in the user's backend).
4. 7g.8 — MCP ask tool (after 7h lays the MCP server framework).

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