Bring every doc up to date, and give the repo a Wi-Fi template that exists

CONTEXT.md had grown by appending and contradicted itself (all four nodes vs six, a retracted CPU
figure, "no calibration", "nobody enrolled", "audio untested as a service", the Wi-Fi-off boot as
not done, a class the tracker replaced). Rewritten as one current-state document organised by
subsystem, with fresh measurements, the owner's decisions, the gotchas, the neck's arrival-day plan
and what is genuinely still open.

README: status, speakers not fitted, new-session note for Hermes, the calibration section (shipped
calibration, coverage hints, outlier dropping, --from-views), running the tests, the docs row.
HANDOFF.md gets a status banner listing where the original brief has drifted. CLAUDE.md starts at
CONTEXT.md. The echo-cancel config no longer talks about a Pi Zero, and the enclosure guide no longer
tells you to centre a servo with a tool that does not exist yet.

pi/network-config.example is a tracked, credentials-free first-boot template: the README pointed at
pi/50-cloud-init.yaml, which is gitignored and so missing from a fresh clone. The dead IdentityCache
(replaced by the tracker) is removed. Docstrings corrected: audio scope publishing, the MCP health
topics, and what the calibration tool does.

Co-Authored-By: Claude Sonnet 5.5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01AFN8nRRCiDiMN7ChBpHJhs

ros/hermes_vision/test/test_tracking.py

@@ -53,3 +53,11 @@ def test_a_stranger_is_unknown_not_named():
 def test_without_an_identifier_nothing_is_named():
     (t,) = FaceTracker().update([f(100)], 0.0)
     assert t.name == '' and t.id == 1
+
+
+def test_iou():
+    from hermes_vision.recognize import iou
+    a = Face(0, 0, 100, 100)
+    assert iou(a, a) == 1.0
+    assert iou(a, Face(200, 200, 50, 50)) == 0.0
+    assert 0.3 < iou(a, Face(50, 0, 100, 100)) < 0.4