agent: lumotia-rebrand — fix QC blockers for phase 0

Phase 0 QC found two real blockers in the baseline commits:

1. crates/llm/src/lib.rs:215 — early-break guard was inverted. The
   guard fired when grammar.is_some() (where grammar already enforces
   shape, making the check redundant) and was disabled for
   grammar.is_none() (the content-tags path that actually needs it).
   Flipped to grammar.is_none() so the JSON-envelope short-circuit
   fires for free-form JSON generation as the commit message
   implied.

2. src/lib/pages/FilesPage.svelte — handleExport() success path had
   no toast, asymmetric with DictationPage which does. Added the
   toasts import and a toasts.success() call after the native save
   so both export surfaces give consistent feedback.

cargo test -p magnotia-llm --lib: 21 pass. npm run check: 0 errors.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

crates/llm/src/lib.rs

@@ -212,7 +212,7 @@ impl LlmEngine {
             generated.push_str(&piece);
             sampler.accept(next);
 
-            if config.grammar.is_some() && json_envelope_complete(&generated) {
+            if config.grammar.is_none() && json_envelope_complete(&generated) {
                 break;
             }