Phase 7: AI-assisted query authoring (autocomplete, explain, fix, optimize, NL translation)

Adds a self-hosted (Ollama, qwen2.5-coder) model provider abstraction
with a pluggable opt-in cloud adapter, schema grounding, and a shared
cost/safety guard every AI-suggested query is assessed against --
compiling to and executing through the same unchanged Phase 2 IR/
compiler and Phase 4 tenant scoping as a hand-written query, no
parallel execution path.

Track A (built into the query bar): inline ghost-text autocomplete,
"Explain this query", "Fix this query" with a diff view, and a
rule-based "Optimize" suggestion. Track B: natural-language-to-query
translation, always a separate review step from execution, with
`sentryctl query --nl` requiring explicit confirmation to run.
Every accepted/dismissed translate-fix-optimize interaction is logged
into the same append-only audit_log table Phase 4 built.

Two real product bugs were found and fixed via live browser
verification (a Svelte effect re-running on every keystroke that
silently cancelled the ghost-text debounce; a ghost-text widget
positioned at document offset 0 instead of the cursor), and a real
costguard logic bug (unbounded-aggregation vs. raw-row) was caught by
its own test suite. New integration tests wire a real Ollama client
through the real HTTP handler against a mock server matching Ollama's
wire contract (hack/mock-ollama), keeping model-quality verification
out of CI as a disclosed, periodic human-run check instead.

See /docs/phase-7-ai-design.md and /docs/phase-7-runbook.md.

web/src/routes/+page.svelte

@@ -23,6 +23,7 @@
 	let columns = $state<string[]>([]);
 	let rows = $state<unknown[][]>([]);
 	let error = $state('');
+	let warnings = $state<string[]>([]);
 	let loading = $state(false);
 	let hasRun = $state(false);
 	let history = $state<HistoryEntry[]>(loadHistory());
@@ -55,10 +56,12 @@
 	async function runQuery() {
 		loading = true;
 		error = '';
+		warnings = [];
 		try {
 			const result = await apiRunQuery(query, language);
 			columns = result.columns ?? [];
 			rows = result.rows ?? [];
+			warnings = result.warnings ?? [];
 			saveHistory({ query, language, at: Date.now() });
 		} catch (e) {
 			error = e instanceof Error ? e.message : String(e);
@@ -98,7 +101,7 @@
 		sheet below. Build reusable queries into a <a href="/dashboards">dashboard</a>.
 	</p>
 
-	<QueryBar bind:query bind:language onRun={runQuery} {loading} />
+	<QueryBar bind:query bind:language onRun={runQuery} {loading} errorMessage={error} {warnings} />
 
 	{#if error}
 		<p class="error">Error: {error}</p>