[AZ-654] [AZ-655] [AZ-656] gimbal_controller primitives + monotonic clock fix (batch 11)

AZ-654 SweepEngine: pendulum default, Raster/LawnMower variants
reserved and explicitly NotImplemented (no silent fallback per AC-3).
Time injected via next_step(now) for deterministic dwell tests.

AZ-655 PlanExecutor: linear yaw/pitch interpolation between PanGoals
with self-throttle (default 50 ms); stats expose
commands_emitted/dropped_to_throttle counters. PanGoal/PanPlan added
to shared::models::gimbal (spec drift: data_model.md §PanPlan flagged
for next doc sync).

AZ-656 CentreOnTarget: zoom-aware proportional control loop (correction
~ 1/zoom); target_lost debounced — fires once per loss streak, resets
on bbox return. Also fixes the misleadingly-named monotonic_ns() helper
introduced by AZ-653 that used SystemTime::now(): GimbalController now
owns a shared::clock::MonoClock and stamps GimbalState::ts_monotonic_ns
via clock.elapsed_ns(). AZ-656 AC-2 forced the correction; integration
test verifies the fix end-to-end.

58/58 gimbal_controller tests green (47 unit + 7 AZ-653 integration +
4 new batch_11 integration). Workspace test suite green this run.

Co-authored-by: Cursor <cursoragent@cursor.com>

crates/shared/src/models/gimbal.rs

@@ -1,4 +1,4 @@
-//! `GimbalState` — per `data_model.md §4 Action / piloting entities`.
+//! `GimbalState` + `PanPlan` — per `data_model.md §4 Action / piloting entities`.
 
 use serde::{Deserialize, Serialize};
 
@@ -10,3 +10,24 @@ pub struct GimbalState {
     pub ts_monotonic_ns: u64,
     pub command_in_flight: bool,
 }
+
+/// One waypoint in a `PanPlan`. `at_ns` is monotonic-nanoseconds since
+/// the plan was loaded (i.e. relative to the plan's clock origin, not
+/// since boot); the executor interpolates between adjacent goals based
+/// on this relative timeline.
+#[derive(Debug, Clone, Copy, PartialEq, Serialize, Deserialize)]
+pub struct PanGoal {
+    pub yaw_deg: f32,
+    pub pitch_deg: f32,
+    pub zoom: f32,
+    pub at_ns: u64,
+}
+
+/// Path-tracking plan emitted by `semantic_analyzer` (via
+/// `scan_controller`) and consumed by `gimbal_controller`. Goals are
+/// ordered strictly increasing in `at_ns`. Empty plans are rejected by
+/// the executor's validate step.
+#[derive(Debug, Clone, PartialEq, Serialize, Deserialize)]
+pub struct PanPlan {
+    pub goals: Vec<PanGoal>,
+}