agent: lumotia-rebrand — fix Codex cross-model review blockers

Codex independent review found 11 blockers post-cascade. All addressed.

CRITICAL (data-loss / crash):

10. crates/core/src/paths.rs — migrate_legacy_data_dir_inner used
    fs::rename which fails with EXDEV when source + target are on
    different filesystems (encrypted-home, bind mounts, separate
    $XDG_DATA_HOME partition). Combined with the Phase 5 QC fix that
    made migration errors fatal, this would crash on first launch
    for any user whose data dir spans filesystems. Added
    rename_or_copy_tree() that falls back to copy_dir_recursive +
    remove_dir_all on CrossesDevices / errno 18 (EXDEV). Symlinks
    preserved verbatim. Same fallback applied to magnotia.db ->
    lumotia.db inside the dir.

11. Added 4 unit tests: copy_dir_recursive preserves nested
    structure, rename_or_copy_tree same-filesystem happy path,
    is_cross_device classifies CrossesDevices kind + raw errno 18.

Doc residuals (blockers 1-9):

1. crates/cloud-providers/Cargo.toml — "Wyrdnote pending rebrand"
   description.
2. crates/cloud-providers/src/provider.rs — module docs + test
   fixture Wyrdnote refs.
3. crates/transcription/src/orchestrator.rs — module docs + test
   fixture Wyrdnote refs.
4. docs/roadmap/2026-05-10-pkm-phase-tooling-shortlist.md — phase
   name + outputs/wyrdnote path refs.
5. docs/architecture-map/04-llm-formatting-mcp/llm-tests.md —
   MAGNOTIA_LLM_TEST_MODEL env var.
6. .../cloud-providers-stubs.md — MAGNOTIA_API_KEY_*.
7. docs/architecture-map/03-audio-transcription/tests-and-fixtures.md
   — MAGNOTIA_WHISPER_*.
8. docs/gpu-tuning/plan.md — MAGNOTIA_BENCH_RUN.
9. docs/superpowers/specs/2026-05-09-battery-gpu-aware-thread-tuning-
   design.md + corresponding plan — MAGNOTIA_POWER_STATE_OVERRIDE,
   MAGNOTIA_INFERENCE_THREADS.

cargo test --workspace: 343 pass / 0 fail (up from 339; +4 EXDEV
fallback tests).

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

docs/superpowers/specs/2026-05-09-battery-gpu-aware-thread-tuning-design.md

@@ -61,7 +61,7 @@ pub fn probe_power_state() -> PowerState;
 
 **TTL cache**: `OnceLock<Mutex<(PowerState, Instant)>>` with 10s TTL. Re-probe on expiry. Battery state changes slowly; 10s is far below human-perceptible latency for thread-count adjustment.
 
-**Test override**: `MAGNOTIA_POWER_STATE_OVERRIDE=ac|battery|unknown` short-circuits the probe. Always-on (not just `cfg(test)`) so `thread_sweep.rs` can drive both states without unplugging hardware. Documented as test-only; users overriding it in production is benign.
+**Test override**: `LUMOTIA_POWER_STATE_OVERRIDE=ac|battery|unknown` short-circuits the probe. Always-on (not just `cfg(test)`) so `thread_sweep.rs` can drive both states without unplugging hardware. Documented as test-only; users overriding it in production is benign.
 
 ### `tuning.rs`
 
@@ -81,8 +81,8 @@ const GPU_FLOOR_LLM: usize = 2;
 const GPU_FLOOR_WHISPER: usize = 4;
 
 pub fn inference_thread_count(workload: Workload, gpu_offloaded: bool) -> usize {
-    // 1. MAGNOTIA_INFERENCE_THREADS env override → absolute bypass
-    if let Ok(s) = std::env::var("MAGNOTIA_INFERENCE_THREADS") {
+    // 1. LUMOTIA_INFERENCE_THREADS env override → absolute bypass
+    if let Ok(s) = std::env::var("LUMOTIA_INFERENCE_THREADS") {
         if let Ok(n) = s.parse::<usize>() {
             if n > 0 { return n; }
         }
@@ -156,15 +156,15 @@ Compile-time feature check (`whisper-vulkan` is in default features) plus runtim
 
 ### Override behaviour
 
-- `MAGNOTIA_INFERENCE_THREADS=N` (existing, unchanged) — absolute bypass. Returns N regardless of power/GPU state. For benchmarking, big-iron desktops, and users who want to opt out.
-- `MAGNOTIA_POWER_STATE_OVERRIDE` — test only.
+- `LUMOTIA_INFERENCE_THREADS=N` (existing, unchanged) — absolute bypass. Returns N regardless of power/GPU state. For benchmarking, big-iron desktops, and users who want to opt out.
+- `LUMOTIA_POWER_STATE_OVERRIDE` — test only.
 - No fine-grained `MAGNOTIA_BATTERY_CLAMP=off` or similar in v1. Add only if real users hit a case where the existing all-or-nothing override is insufficient.
 
 ## Tests
 
 ### Existing test extended
 
-`crates/transcription/tests/thread_sweep.rs` already runs the JFK clip across n_threads values and prints an RTF table. Extend to four blocks driven by `MAGNOTIA_POWER_STATE_OVERRIDE`:
+`crates/transcription/tests/thread_sweep.rs` already runs the JFK clip across n_threads values and prints an RTF table. Extend to four blocks driven by `LUMOTIA_POWER_STATE_OVERRIDE`:
 
 ```
 === n_threads scaling: AC, CPU ===
@@ -181,7 +181,7 @@ Each block uses the same `n_threads` sweep `[1, 2, 4, 6, 8, 12]` and reports xc_
 
 - `battery_clamp_halves_on_battery` — set override to battery, assert returned value is roughly half of AC.
 - `gpu_floor_lower_for_llm_than_whisper` — both with `gpu_offloaded=true`, assert Llm ≤ Whisper.
-- `env_var_bypasses_all_clamps` — set `MAGNOTIA_INFERENCE_THREADS=10`, set battery, set gpu_offloaded; assert returns 10.
+- `env_var_bypasses_all_clamps` — set `LUMOTIA_INFERENCE_THREADS=10`, set battery, set gpu_offloaded; assert returns 10.
 - `clamp_to_min_when_low_core_count` — fall through to min on 1-2 logical cores via available_parallelism (use a mock or just verify clamp inside the function).
 - `clamp_to_max_for_huge_machines` — assert MAX_INFERENCE_THREADS=8 still binds.