refactor(commit-ai): remove local models and simplify AI flow

Remove local on-device model support and related IPC commands,
consolidating commit-generation to cloud providers and simplifying the
AI crate surface. Local-specific types, generation profiles, caching,
and the local prompt builder were removed while message sanitization and
diff-echo detection were preserved. Also harden repository handling and
runtime: unborn HEADs are handled gracefully so empty repos still report
files, Git LFS sync is skipped for repositories without commits, and
tokio runtime features were enabled.

- Remove local model engine, load/status commands, and local profile code
- Handle unborn HEAD and skip LFS sync for repos without commits
- Enable tokio runtime features and route AI generation to cloud only

src/lib/components/CommitPanel.svelte

@@ -1,6 +1,5 @@
 <script lang="ts">
   import { Check, GitCommitHorizontal, LoaderCircle, RotateCcw, Settings, ShieldCheck, Sparkles } from "@lucide/svelte";
-  import type { CommitAiPhase, CommitAiProvider } from "../types";
 
   interface Props {
     commitMessage: string;
@@ -10,8 +9,6 @@
     isBusy: boolean;
     operation: string;
     stagedCount: number;
-    commitAiProvider: CommitAiProvider;
-    commitAiPhase: CommitAiPhase;
     commitAiGenerating: boolean;
     commitAiReviewing: boolean;
     commitAiSplitting: boolean;
@@ -35,8 +32,6 @@
     isBusy = false,
     operation = "",
     stagedCount = 0,
-    commitAiProvider = "local",
-    commitAiPhase = "idle",
     commitAiGenerating = false,
     commitAiReviewing = false,
     commitAiSplitting = false,
@@ -57,23 +52,19 @@
     onCommit();
   }
 
-  function aiButtonTitle(provider: CommitAiProvider, phase: CommitAiPhase, staged: number): string {
+  function aiButtonTitle(staged: number): string {
     if (staged === 0) return "Stage changes first";
-    if (provider === "local" && phase === "loading") return "AI model is downloading/loading — this happens once";
-    if (provider === "local" && phase === "error") return "AI model failed to load — check AI settings";
     return "Generate commit message with AI from the staged diff";
   }
 
-  let localModelLoading = $derived(commitAiProvider === "local" && commitAiPhase === "loading");
   let canGenerate = $derived(
     hasRepository &&
     !isBusy &&
     !commitAiGenerating &&
     !commitAiReviewing &&
-    stagedCount > 0 &&
-    (commitAiProvider !== "local" || commitAiPhase === "ready"),
+    stagedCount > 0,
   );
-  let canReview = $derived(canGenerate && commitAiProvider !== "local");
+  let canReview = $derived(canGenerate);
   let canSplit = $derived(canReview && stagedCount > 1 && !commitAiSplitting);
 </script>
 
@@ -90,7 +81,7 @@
         type="button"
         onclick={onSplitStaged}
         disabled={!canSplit}
-        title={commitAiProvider === "local" ? "Commit splitting currently requires an API provider" : "Suggest logical commits for the staged files"}
+        title="Suggest logical commits for the staged files"
       >
         {#if commitAiSplitting}<LoaderCircle class="spin" size={14} aria-hidden="true" />{:else}<GitCommitHorizontal size={14} aria-hidden="true" />{/if}
         Split
@@ -100,7 +91,7 @@
         type="button"
         onclick={onReviewStaged}
         disabled={!canReview}
-        title={commitAiProvider === "local" ? "Pre-commit review currently requires an API provider" : stagedCount === 0 ? "Stage changes first" : "Review staged changes for bugs and risks"}
+        title={stagedCount === 0 ? "Stage changes first" : "Review staged changes for bugs and risks"}
       >
         {#if commitAiReviewing}<LoaderCircle class="spin" size={14} aria-hidden="true" />{:else}<ShieldCheck size={14} aria-hidden="true" />{/if}
         Review
@@ -110,9 +101,9 @@
         type="button"
         onclick={onGenerateCommitMessage}
         disabled={!canGenerate}
-        title={aiButtonTitle(commitAiProvider, commitAiPhase, stagedCount)}
+        title={aiButtonTitle(stagedCount)}
       >
-        {#if commitAiGenerating || localModelLoading}<LoaderCircle class="spin" size={14} aria-hidden="true" />{:else}<Sparkles size={14} aria-hidden="true" />{/if}
+        {#if commitAiGenerating}<LoaderCircle class="spin" size={14} aria-hidden="true" />{:else}<Sparkles size={14} aria-hidden="true" />{/if}
         Generate
       </button>
       <button class="commit-settings-button" type="button" onclick={onOpenAiSettings} disabled={isBusy} title="AI settings" aria-label="AI settings">