fix(embodiments): restore omission detection in verify script; correct migration formula in docs

Address Codex review feedback on #308:

- verify_embodiment_structure.sh validated whatever list_presets()
  returned, so an accidentally dropped preset file (e.g. quadcopter,
  which has no configs/ dev copy) passed the preflight silently. Keep a
  required-minimum set checked as a SUBSET of what ships: omissions fail
  the check, while new presets still validate automatically without
  editing the script.
- schema.json description and docs/embodiment_schema.md documented the
  legacy fractional rtc_execution_horizon migration as int(v x
  chunk_size) (truncation), but EmbodimentConfig.from_dict() rounds:
  round(v x chunk_size), minimum 1. Document the actual behavior
  (v=0.25, chunk_size=30 migrates to 8, not 7). No behavior change; the
  shipped presets' migrated values are unaffected.

Author: gaolebaigao

docs/embodiment_schema.md

@@ -83,7 +83,7 @@ List of camera streams the model expects (1–8 cameras).
 |---|---|---|---|
 | `frequency_hz` | float | 0–1000 (exclusive 0) | Robot control loop rate. |
 | `chunk_size` | int | 1–200 | Actions in a single inference chunk. |
-| `rtc_execution_horizon` | int | 1–`chunk_size` | Integer count of actions to lock during RTC replan. Legacy fractional values (0 < v < 1) auto-migrate to `int(v × chunk_size)` at load with a one-time deprecation warning; schema v2 will reject them. |
+| `rtc_execution_horizon` | int | 1–`chunk_size` | Integer count of actions to lock during RTC replan. Legacy fractional values (0 < v < 1) auto-migrate to `round(v × chunk_size)` (minimum 1) at load with a one-time deprecation warning; schema v2 will reject them. |
 
 **Cross-field rules (warnings, not blocking):**
 - `rtc_execution_horizon < 1` (else `rtc-horizon-too-short` warning — RTC degenerates below one action)

scripts/verify_embodiment_structure.sh

@@ -42,11 +42,16 @@ from tether.embodiments import EmbodimentConfig, list_presets
 from tether.embodiments.validate import validate_embodiment_config
 
 presets = list_presets()
-# Don't hard-code the expected preset list — it already drifted once when
-# quadcopter shipped, and hard-coding it here would break again on the
-# next preset. Validate whatever the package actually ships.
-if not presets:
-    print("  ✗ list_presets() returned no presets — package presets dir missing?")
+# Two checks, not one: a required-minimum SUBSET (catches an accidentally
+# dropped preset file — an equality check broke when quadcopter shipped,
+# but no check at all lets packaging omissions pass silently) plus dynamic
+# validation of everything else that ships. New presets validate
+# automatically in the loop below; add them to REQUIRED when they should
+# be omission-protected too.
+REQUIRED = {"franka", "so100", "ur5", "quadcopter"}
+missing = REQUIRED - set(presets)
+if missing:
+    print(f"  ✗ required package presets missing: {sorted(missing)}")
     sys.exit(1)
 
 for name in presets:

src/tether/embodiments/schema.json

@@ -168,7 +168,7 @@
           "type": "number",
           "minimum": 0,
           "maximum": 1000,
-          "description": "Integer count of actions to lock during RTC replan. Per ADR 2026-04-25-auto-calibration-architecture decision #8. Legacy fractional values (0 < value < 1) auto-migrate to int(value * chunk_size) at load time with a one-time deprecation warning. Schema v2 will reject fractional values."
+          "description": "Integer count of actions to lock during RTC replan. Per ADR 2026-04-25-auto-calibration-architecture decision #8. Legacy fractional values (0 < value < 1) auto-migrate to round(value * chunk_size), minimum 1, at load time with a one-time deprecation warning. Schema v2 will reject fractional values."
         }
       }
     },