Fix throttle-detent Abs() macro bug + KB analog-throttle + slide diagnostics (task #50)

Uncommitted work from the speed-model + peer-motion investigation:
 - btl4mppr.cpp: the L4MechControlsMapper full-throttle detent used the
   unparenthesized Abs() macro (STYLE.H:118) on an expression -- Abs(throttlePos
   - 1.0f) mis-expands to -(throttlePos + 1.0f), always <= 0.05, so the detent
   snapped throttle to full EVERY frame.  Diff into a temp first (same class as
   the 7615ecd angular-resync Abs fix).
 - context/pod-hardware.md: document the decomp-verified analog-continuous pod
   throttle path (RIO Ranger 0-800 counts, 0.05 deadband, no notching; '5 speeds'
   is false) from workflow w0odszxro.
 - mech4.cpp: BT_SLIDE/[mslide] per-frame slide diagnostics (peer position moving
   while legs in stand; master decel profile) -- used to prove the stop-slide is a
   peer leg-SM-winds-down-early desync, not master momentum.  Env-gated.

The 'pretty good' coupled-motion gameplay state is already shipped (a9ab3db).

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

context/pod-hardware.md

@@ -25,6 +25,36 @@ to keyboard/gamepad on a dev box; real wiring is a pod bring-up task (Phase 8).
 model — `LBE4ControlsManager` groups are fed by all devices (RIO on the pod, DirectInput on dev);
 the `MechControlsMapper` interprets them ([[locomotion]]). [T2]
 
+### The pod throttle is ANALOG-CONTINUOUS, not notched (verified end-to-end) [T1]
+The authentic pod throttle path — traced 2026-07 (task #50 throttle-fidelity question):
+1. **Hardware → RIO:** serial `AnalogReply` packet → `Ranger("Throttle", 0, 800, .05)` — raw counts
+   0–800, 5% deadband, auto-ranging offset, output a CONTINUOUS Scalar; the sign is inverted
+   ("Throttle counts BACKWARDS", `engine/MUNGA_L4/L4RIO.cpp:1374-1377`, Ranger @L4RIO.cpp:461-701).
+   No quantization/notching anywhere in `Ranger::Update`.
+2. **Manager:** `LBE4ControlsManager::Execute` → `scalarGroup[ScalarThrottle].Update(&rioPointer->
+   Throttle, mode_mask)` on every AnalogReply (`L4CTRL.cpp:1379-1382`). ScalarThrottle = index 0 →
+   manager+0x24 (scalarGroup base 0x24, 0x20/entry; buttonGroup base 0x1c0, keyboardGroup 0x160).
+3. **Streamed `.CTL` mapping (the "handled elsewhere"):** `MechRIOMapper`'s ctor @004d266c binds NO
+   throttle — the bind comes from the type-19 `ControlMappingStream` resource named **"L4"** (child
+   of the per-mech type-6 `ControlMappingsList`; installed by `BTL4APP MakeViewpointEntity` via
+   `CreateStreamedMappings` @0047703c). BTL4.RES "L4" record [1]:
+   `Scalar Throttle → subsystemID 0 (ControlsMapper slot), DirectMapping, attr 4, mask 0xffffffff`.
+   Attr 4 = "ThrottlePosition" @ mapper+0x11c (binary IndexEntry table @0050efd8: id 4 → offset
+   0x11d-1 = 0x11c, name "ThrottlePosition" @0050f28f). Reverse = record [2]: `Button Throttle1
+   (0x3F, on the throttle handle) → attr 6 ReverseThrust@0x124`. Turn = pedals value-bound in the
+   ctor (manager+0x44/+0x64 → mapper+0x1b4/+0x1b8).
+4. **Interpretation:** `L4MechControlsMapper::InterpretControls` @004d196c applies the ONLY software
+   detent — snap to 1.0 when |t−1.0| ≤ 0.05 — then `MechControlsMapper::InterpretControls` @004afd10
+   computes `speedDemand@0x128 = maxSpeed(mech+0x34c) × throttlePosition(0x11c) × scale(mech+0x5c0)`
+   (forward) or `−maxSpeed × throttlePosition` (reverse flag 0x124).
+
+**Consequence:** the original pod produced a continuously varying speedDemand while the lever moved
+(updated per serial AnalogReply, NOT per render frame). There are NO "5 throttle notches" anywhere
+in the software path. (Keyboard keys '1'-'5' in @004d1bf0 set controls-manager MODE masks; the
+'+'/'-' pair steps a [0,5] value that drives `pow(2,x)` into mech+0x404 = HUD zoom 1×–32× — neither
+is a speed setting.) The mech's `throttleState@0x4a4` writer remains un-exported (likely in the
+0x4a9b5a–0x4ab188 gap) — [[open-questions]].
+
 ## Multi-surface gauge path (intact, pod-only by default)
 The pod multi-surface path EXISTS and is intact: `DPLRenderer::FindBestAdapterIndices` (multi-
 adapter selector, honors PRIMGAUGE/SECGAUGE/MFDGAUGE/SPANDISABLE), `SVGA16::BuildWindows` (a