feat(sim): analytical Left HUD redesign + affect channel + no-cache

Left-brain HUD look-and-feel pass (judged by eye in the sim):
- corner-bracket targeting reticles (capped arms) replace plain boxes
- translucent label chips, legible over any frame
- two sensor channels: cyan detections (with deterministic confidence
  scores) vs amber measurements (center crosshair)
- bbox-sized "ANALYSIS . L{n} . {k} OBJ" status tag, escalating with Left

Affect channel (emotions in the HUD), per
docs/superpowers/specs/2026-06-22-affect-channel-hud-design.md:
- surfaces only when BOTH knobs up; strength = min(left, right)
- stable per-scene palette, more words appear with combined strength
- soft glowing violet words on their own opacity layer (the dream
  leaking into the machine's read); math in player/alteration.py
- forest/cosmos/abyss palettes in the manifest; 5 new unit tests

Simulator no-cache middleware so by-eye iteration never serves a stale
app.js / api response (fixes the latent "plan has affect but clip.affect
empty" stale-/api/clips bug).

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

docs/superpowers/specs/2026-06-22-affect-channel-hud-design.md

@@ -0,0 +1,85 @@
+# Affect channel — emotions in the Left-brain HUD
+
+**Status:** approved (session 0013, 2026-06-22)
+**Surface:** simulator preview (`simulator/`, `player/alteration.py`)
+**Builds on:** the machine-altered-perception design SPEC; the Left HUD look-and-feel
+pass (same session).
+
+## Idea
+
+A third HUD channel beside the cyan *detections* and amber *measurements*: soft,
+glowing **emotion-words** that surface the feelings the experience may invoke.
+They appear only when *both* the analytical (Left) and dreamlike (Right) knobs are
+up — the dream leaking into the machine's reading. This is the uncanny edge of the
+thesis: the machine trying to quantify not just what is there, but how you are
+meant to feel.
+
+## Behaviour
+
+- **Trigger / intensity.** Affect strength = `min(left, right)` (0–4). Either knob
+  at 0 → no emotions at all. Opacity scales with that strength × `overlay_gain`.
+- **Escalation.** A **stable emotional palette per scene** — higher combined
+  strength reveals *more* words at higher opacity. Each word carries a `min_level`
+  (the same mechanic the detection channel uses), but compared against the
+  *combined* `min(left, right)` strength rather than Left alone.
+- **Rendering.** Floating words at authored scene positions — **no boxes or
+  reticles**, lowercase, semi-transparent with a soft glow, in a distinct **violet**
+  register so they read as affective and clearly *softer* than the hard clinical
+  reticles.
+
+## Where the math lives
+
+Consistent with the existing split (alteration math in Python, label-selection in
+the client):
+
+- `player/alteration.py` gains an `AffectOverlay(strength, intensity)` on the
+  `RenderPlan`. `strength = min(left, right)`; `intensity = clamp(overlay_gain *
+  min(left,right) / KNOB_MAX, 0, 1)`. Returned in `render_plan_to_dict` under
+  `"affect"`. Pure, unit-tested.
+- The simulator client picks *which* words to show by comparing each affect
+  entry's `min_level` to `plan.affect.strength`, and renders them at
+  `plan.affect.intensity` opacity.
+
+`is_identity` is unaffected: `min(left,right) > 0` implies `left > 0`, which already
+makes `overlay.level > 0`.
+
+## Data
+
+New optional per-clip `affect` list in the manifest, parallel to `annotations`:
+
+```json
+"affect": [
+  {"key": "feel.awe", "at": [0.5, 0.4], "min_level": 1},
+  {"key": "feel.serenity", "at": [0.2, 0.62], "min_level": 2}
+],
+"strings": {"en": {"feel.awe": "awe", "feel.serenity": "serenity"}}
+```
+
+`at` is a normalized `[x, y]` anchor point (not a box — feelings are scene-level).
+The words live in the existing `strings.en` map. `Clip` gains an `affect` field
+(defaulting to `[]`) threaded through `_clip_from_dict` and `to_dict`.
+
+Starter palettes (words are art-direction, easily tuned):
+
+| scale  | palette (min_level 1 → 4)                     |
+|--------|-----------------------------------------------|
+| forest | awe · serenity · reverence · stillness        |
+| cosmos | wonder · vastness · insignificance · longing  |
+| abyss  | unease · fascination · isolation · dread      |
+
+All three scales carry the data; forest is fully realized (it has the real Right
+variants).
+
+## Testing
+
+- Python unit tests: affect `strength = min(left, right)` across knob combos;
+  intensity scaling and `overlay_gain`; `0` when either knob is 0; presence in the
+  serialized plan.
+- By-eye in the live simulator (forest, Left & Right both up) — the established
+  judge-by-eye loop for this surface.
+
+## Out of scope
+
+- No drift-toward-unsettling arc (rejected in favour of a stable palette).
+- No per-object emotion tags; no animated drift (words are statically placed for
+  v1; gentle motion can come later if wanted).