feat(calibration): ADR-151 Stages 2–5 — enrollment, extraction, specialist bank, runtime

New crate wifi-densepose-calibration implementing the per-room pipeline beyond
Stage-1 baseline:

- anchor.rs: guided-anchor sequence + event-sourced EnrollmentSession (Stage 2)
- enrollment.rs: AnchorQualityGate + AnchorRecorder — gates anchors against the
  ADR-135 baseline deviation (presence/motion), re-prompts bad captures
- extract.rs: Features + AnchorFeature — autocorrelation periodicity (breathing/
  HR bands), variance/motion (Stage 3)
- specialist.rs: 6 small room-calibrated models — presence (learned threshold),
  posture (nearest-prototype), breathing/heartbeat (band periodicity),
  restlessness (calm/active normalization), anomaly (novelty vs anchors) (Stage 4)
- bank.rs: SpecialistBank — train/persist + baseline-drift STALE invalidation
- runtime.rs: MixtureOfSpecialists — presence short-circuit + anomaly veto +
  stale flagging (Stage 5)

Statistical heads make the pipeline runnable/validatable today; the ADR-150 HF
RF Foundation Encoder backbone is the documented upgrade path. 29 unit tests pass.

Co-Authored-By: claude-flow <ruv@ruv.net>

v2/crates/wifi-densepose-calibration/src/error.rs

@@ -0,0 +1,49 @@
+//! Error types for the calibration pipeline.
+
+use thiserror::Error;
+
+/// Errors surfaced by the per-room calibration & training pipeline (ADR-151).
+#[derive(Debug, Error)]
+pub enum CalibrationError {
+    /// An anchor was recorded with zero frames.
+    #[error("anchor '{0}' captured no frames")]
+    EmptyAnchor(String),
+
+    /// The enrollment session is missing anchors required to train a specialist.
+    #[error("enrollment incomplete: missing anchors {missing:?}")]
+    IncompleteEnrollment {
+        /// Labels still required.
+        missing: Vec<String>,
+    },
+
+    /// A frame did not match the expected tier geometry.
+    #[error("frame geometry mismatch: {0}")]
+    Geometry(String),
+
+    /// Not enough samples to fit a specialist.
+    #[error("insufficient samples for '{kind}': have {have}, need {need}")]
+    InsufficientSamples {
+        /// Specialist kind.
+        kind: String,
+        /// Samples available.
+        have: usize,
+        /// Samples required.
+        need: usize,
+    },
+
+    /// Serialization / persistence failure.
+    #[error("serialization error: {0}")]
+    Serde(String),
+
+    /// The specialist bank was trained against a different baseline and is stale.
+    #[error("bank is STALE: trained against baseline {trained}, current is {current}")]
+    StaleBaseline {
+        /// Baseline id the bank was trained against.
+        trained: String,
+        /// Current baseline id.
+        current: String,
+    },
+}
+
+/// Convenience result alias.
+pub type Result<T> = std::result::Result<T, CalibrationError>;