docs: record hendi remote-control lockout findings for firmware v1.12

Baseline for the planned firmware fix: reset/reconnect don't clear the
ungraceful-disconnect lockout, only a physical power cycle does.

Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01GpePKZiEZWbGo9HrfuML6U

docs/hendi_lockout_findings.md

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+# Hendi remote-control lockout findings
+
+Firmware under test: **v1.12** (`getSoftwareVersion()` / `I?`+`V?` via
+`components/actor/hendiCtrl.py`). Reproduced and verified on real hardware
+using `scripts/hendi_ctrl_app.py`'s `--trigger-error-state`, `--reset` and
+`--test-heater` flags.
+
+## Trigger
+
+Calling `remoteEnable(True)` (`R1`) and then disconnecting/exiting without a
+matching `remoteEnable(False)` (`R0`) - i.e. an ungraceful disconnect while
+remote control is enabled - puts the device into a locked-out state.
+
+## Recovery attempts
+
+| # | Recovery method | Mechanism | Result |
+|---|---|---|---|
+| 1 | `--reset` (toggle DTR/RTS reset line) | Soft reset via serial control lines, no power loss | **Fails** - `remoteEnable(True)` still returns `HendiException("Communication error")` on the next connection |
+| 2 | `--reset` immediately followed by `--test-heater` in the *same* process/connection | Soft reset, then reuse the still-open serial connection | Succeeded once, but not reproducible across repeat isolated attempts - not a reliable recovery path |
+| 3 | Physical power cycle (device knob) | Full power-off/on of the unit | **Recovers** - `remoteEnable(True)` succeeds immediately afterward, heater sweep runs cleanly |
+
+## Symptom while locked out
+
+- `I?` / `V?` (software identifier/version queries) still respond normally.
+- `R1` (`remoteEnable(True)`) fails with a communication error - this is the
+  only observed symptom, and it blocks any command path that needs remote
+  control enabled (e.g. `--test-heater`).
+
+## Conclusion
+
+On firmware v1.12, only a physical power cycle clears the lockout; neither a
+serial soft-reset nor a fresh serial reconnect does. This is the behavior the
+planned firmware fix should address - a graceful-disconnect timeout, an
+explicit unlock command, or making the DTR/RTS reset line actually clear the
+lockout flag.