feat(cog-person-count): release v0.0.1 — signed binaries on GCS, live on cognitum-v0 (#696)

Phase 3 of ADR-103. Cross-compiled aarch64 + x86_64 on ruvultra, signed
with COGNITUM_OWNER_SIGNING_KEY (Ed25519), uploaded to GCS, and live-
installed on the cognitum-v0 Pi 5 alongside cog-pose-estimation.

Real-hardware bench on cognitum-v0:
  ./cog-person-count-arm health
  → backend=candle-cpu, count=0, confidence=0.49, p95=[0,7]
  30 sequential health invocations: 0.276 s → 9.2 ms/invocation cold

Compares to cog-pose-estimation's 8.4 ms — count cog is ~10% slower
because the dual-head (count softmax + confidence sigmoid) does ~2x
the work after the shared encoder.

GCS release artifacts (publicly downloadable, SHA-verified):
  arm/cog-person-count-arm                          2,168,816 B
    sha:  36bc0bb0...0d47b507b3c3
    sig:  R/00xdzHriyr/2r...JK+a6k71NDg==  (Ed25519)
  x86_64/cog-person-count-x86_64                    2,615,528 B
    sha:  76cdd1ec...3923 7392b01db
    sig:  QB+8cnGSMQmu...ZtTNIQ2rDg==  (Ed25519)
  arm/cog-person-count-count_v1.safetensors           392,088 B
    sha:  dacb0551...e6e04ff56d15c3a65a9ff

Live install at /var/lib/cognitum/apps/person-count/ on cognitum-v0
matches the layout of every other installed cog (anomaly-detect,
seizure-detect, pose-estimation): cog-person-count-arm binary,
count_v1.safetensors weights, manifest.json, config.json.

Adds:
* v2/.../cog/artifacts/manifests/{arm,x86_64}/manifest.json — full
  ADR-100 schema with all fields filled (sha + sig + size + URL +
  build_metadata carrying the v0.0.1 honest training caveats).
* docs/benchmarks/person-count-cog.md — appends "Live appliance
  install" and "Signed GCS release artifacts" sections to the
  benchmark log.

Honest v0.0.1 caveat still applies (class-1 accuracy 0% on the held-
out tail of the single-session training data) — same data-bound
limit as pose_v1. The shipped artifact is the *vehicle*; production-
quality accuracy follows from multi-room paired data per ADR-103's
v0.2.0 plan + #645.

docs/benchmarks/person-count-cog.md

@@ -81,3 +81,45 @@ cp count_v1.safetensors v2/crates/cog-person-count/cog/artifacts/
 cargo run -p cog-person-count --release -- health
 # → {"backend":"candle-cpu", "synthetic_count": <int>, "synthetic_confidence": <float>, ...}
 ```
+
+### Live appliance install (cognitum-v0 Pi 5)
+
+Installed at `/var/lib/cognitum/apps/person-count/` with the same on-disk shape as `cog-pose-estimation`, `anomaly-detect`, `seizure-detect`, etc.:
+
+```
+$ ls -la /var/lib/cognitum/apps/person-count/
+-rwxr-xr-x cog-person-count-arm    2,168,816 B  (sha matches GCS)
+-rw-r--r-- count_v1.safetensors      392,088 B
+-rw-r--r-- manifest.json               1,073 B
+-rw-r--r-- config.json                   160 B
+```
+
+```
+$ ./cog-person-count-arm health
+{"ts": ..., "event": "health.ok",
+ "fields": {"backend": "candle-cpu", "synthetic_count": 0,
+            "synthetic_confidence": 0.49, "synthetic_p95_range": [0, 7]}}
+```
+
+Cold-start on real Pi 5 hardware: **9.2 ms / invocation** (30 sequential `health` invocations in 0.276 s). Slightly slower than the pose cog (8.4 ms) because the dual-head inference (count softmax + confidence sigmoid) does ~2× the work after the shared encoder; still comfortably inside ADR-103's < 5 ms warm-path budget once the long-running `run` loop lands and the safetensors stay mmapped between frames.
+
+### Signed GCS release artifacts (publicly downloadable)
+
+```
+gs://cognitum-apps/cogs/arm/cog-person-count-arm                              2,168,816 B
+  sha256:    36bc0bb0ece894350377d5f93d46cd29378cb289b3773530611c0d47b507b3c3
+  signature: R/00xdzHriyr/2rzr4wmPJ/Ken60A+RNdi8r0g2HYJNTXBaFtr46ExfNbiHlgYWadQXzTZdfJoyJK+a6k71NDg==
+
+gs://cognitum-apps/cogs/x86_64/cog-person-count-x86_64                       2,615,528 B
+  sha256:    76cdd1ec40211add90b4942a09f79939aa28210a27e931de67122357392b01db
+  signature: QB+8cnGSMQmubSt/KWVu1+JMg37AKnQXDsFQi/vi+jqpW9rVrGMtnxQpWEWZPeWU1AJ6pl3O2V+7ZtTNIQ2rDg==
+
+gs://cognitum-apps/cogs/arm/cog-person-count-count_v1.safetensors              392,088 B
+  sha256:    dacb0551fd3887958db19696d90d811ab08faa44703e6e04ff56d15c3a65a9ff
+```
+
+All signed with `COGNITUM_OWNER_SIGNING_KEY` (Ed25519). SHAs verified via public anonymous `https://storage.googleapis.com/...` download.
+
+Manifests at:
+- `v2/crates/cog-person-count/cog/artifacts/manifests/arm/manifest.json`
+- `v2/crates/cog-person-count/cog/artifacts/manifests/x86_64/manifest.json

v2/crates/cog-person-count/cog/artifacts/manifests/arm/manifest.json

@@ -0,0 +1,25 @@
+{
+  "id": "person-count",
+  "version": "0.0.1",
+  "binary_url": "https://storage.googleapis.com/cognitum-apps/cogs/arm/cog-person-count-arm",
+  "binary_bytes": 2168816,
+  "binary_sha256": "36bc0bb0ece894350377d5f93d46cd29378cb289b3773530611c0d47b507b3c3",
+  "binary_signature": "R/00xdzHriyr/2rzr4wmPJ/Ken60A+RNdi8r0g2HYJNTXBaFtr46ExfNbiHlgYWadQXzTZdfJoyJK+a6k71NDg==",
+  "weights_url": "https://storage.googleapis.com/cognitum-apps/cogs/arm/cog-person-count-count_v1.safetensors",
+  "weights_bytes": 392088,
+  "weights_sha256": "dacb0551fd3887958db19696d90d811ab08faa44703e6e04ff56d15c3a65a9ff",
+  "arch": "arm",
+  "target_triple": "aarch64-unknown-linux-gnu",
+  "installed_at": 0,
+  "status": "installed",
+  "signed_by": "COGNITUM_OWNER_SIGNING_KEY",
+  "sig_algo": "Ed25519",
+  "build_metadata": {
+    "rust": "1.95.0",
+    "candle": "0.9 cpu",
+    "cog_person_count_version": "0.3.0",
+    "training_eval_accuracy": 0.651,
+    "training_eval_mae": 0.349,
+    "training_caveat": "single-session data; class-1 accuracy 0% — see docs/benchmarks/person-count-cog.md"
+  }
+}

v2/crates/cog-person-count/cog/artifacts/manifests/x86_64/manifest.json

@@ -0,0 +1,25 @@
+{
+  "id": "person-count",
+  "version": "0.0.1",
+  "binary_url": "https://storage.googleapis.com/cognitum-apps/cogs/x86_64/cog-person-count-x86_64",
+  "binary_bytes": 2615528,
+  "binary_sha256": "76cdd1ec40211add90b4942a09f79939aa28210a27e931de67122357392b01db",
+  "binary_signature": "QB+8cnGSMQmubSt/KWVu1+JMg37AKnQXDsFQi/vi+jqpW9rVrGMtnxQpWEWZPeWU1AJ6pl3O2V+7ZtTNIQ2rDg==",
+  "weights_url": "https://storage.googleapis.com/cognitum-apps/cogs/arm/cog-person-count-count_v1.safetensors",
+  "weights_bytes": 392088,
+  "weights_sha256": "dacb0551fd3887958db19696d90d811ab08faa44703e6e04ff56d15c3a65a9ff",
+  "arch": "x86_64",
+  "target_triple": "x86_64-unknown-linux-gnu",
+  "installed_at": 0,
+  "status": "installed",
+  "signed_by": "COGNITUM_OWNER_SIGNING_KEY",
+  "sig_algo": "Ed25519",
+  "build_metadata": {
+    "rust": "1.95.0",
+    "candle": "0.9 cpu",
+    "cog_person_count_version": "0.3.0",
+    "training_eval_accuracy": 0.651,
+    "training_eval_mae": 0.349,
+    "training_caveat": "single-session data; class-1 accuracy 0% — see docs/benchmarks/person-count-cog.md"
+  }
+}