agent: lumotia-rebrand — fix QC blockers for phase 2

Phase 2 QC found three explicit blockers + a broader sweep needed:

Explicit (QC-named):
- crates/mcp/src/lib.rs:15 — SERVER_NAME public MCP wire identity
- crates/transcription/build.rs:59 — panic message prefix
- crates/llm/tests/content_tags_smoke.rs:7 — docstring -p flag

Swept (string literals + dev env vars + doc comments + test fixtures):
- crates/mcp/src/main.rs — eprintln log prefixes
- src-tauri/src/commands/diagnostics.rs — diagnostic filename + MAGNOTIA_VERSION
- src-tauri/src/commands/audio.rs — recording filename pattern lumotia-<secs>-...wav
- src-tauri/src/commands/fs.rs — test placeholder path
- crates/transcription/src/model_manager.rs — .lumotia-verified marker
- crates/storage/src/database.rs — lumotia-storage-ro-<pid> temp dirs + doc comments
- crates/cloud-providers/src/keystore.rs — LUMOTIA_API_KEY_<PROVIDER> env var
- crates/audio/src/{wav,decode}.rs — lumotia_test_* / lumotia_decode_* test fixtures
- crates/core/src/tuning.rs — LUMOTIA_INFERENCE_THREADS env var
- All MAGNOTIA_LLM_TEST_MODEL / MAGNOTIA_WHISPER_TEST_* env vars
- Doc comments referencing crate names

Excluded (intentional Phase 4/5 scope):
- magnotia_preferences, magnotia_history, magnotia_morning_triage_last_shown
  DB setting keys (Phase 5 paths.rs migration)
- magnotia_startup tracing target (Phase 4)
- crates/core/src/paths.rs (Phase 5 wholesale rewrite + migration shim)

cargo build --workspace passes. cargo test --workspace: 330 pass, 0 fail.

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

crates/transcription/tests/whisper_rs_smoke.rs

@@ -1,17 +1,17 @@
 //! Smoke test: whisper-rs 0.16 loads a GGUF model, transcribes silence, and
 //! accepts set_initial_prompt without panicking.
 //!
-//! Runs only when `MAGNOTIA_WHISPER_TEST_MODEL` is set to the path of a
+//! Runs only when `LUMOTIA_WHISPER_TEST_MODEL` is set to the path of a
 //! ggml/gguf whisper model on disk. Otherwise the test exits quiet.
 
 use std::env;
 
 #[test]
 fn whisper_rs_smoke_loads_and_transcribes() {
-    let model_path = match env::var("MAGNOTIA_WHISPER_TEST_MODEL") {
+    let model_path = match env::var("LUMOTIA_WHISPER_TEST_MODEL") {
         Ok(p) => p,
         Err(_) => {
-            eprintln!("MAGNOTIA_WHISPER_TEST_MODEL not set — skipping");
+            eprintln!("LUMOTIA_WHISPER_TEST_MODEL not set — skipping");
             return;
         }
     };