feat(related): add semantic similarity discovery command

Implement `lore related` command for discovering semantically similar entities
using vector embeddings. Supports two modes:

Entity mode:
  lore related issues 42     # Find entities similar to issue #42
  lore related mrs 99        # Find entities similar to MR !99

Query mode:
  lore related "auth bug"    # Find entities matching free text query

Key features:
- Uses existing embedding infrastructure (nomic-embed-text via Ollama)
- Computes shared labels between source and results
- Shows similarity scores as percentage (0-100%)
- Warns when all results have low similarity (<30%)
- Warns for short queries (<=2 words) that may produce noisy results
- Filters out discussion/note documents, returning only issues and MRs
- Handles orphaned documents gracefully (skips if entity deleted)
- Robot mode JSON output with {ok, data, meta} envelope

Implementation details:
- distance_to_similarity() converts L2 distance to 0-1 score: 1/(1+distance)
- Uses saturating_add/saturating_mul for overflow safety on limit parameter
- Proper error handling for missing embeddings ("run lore embed first")
- Project scoping via -p flag with fuzzy matching

CLI integration:
- Added to autocorrect.rs command registry
- Added Related variant to Commands enum in cli/mod.rs
- Wired into main.rs with handle_related()

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

src/cli/autocorrect.rs

@@ -183,6 +183,7 @@ const COMMAND_FLAGS: &[(&str, &[&str])] = &[
             "--max-evidence",
         ],
     ),
+    ("related", &["--limit", "--project"]),
     (
         "who",
         &[