fix(session): Clear the last run's jobs and session before starting

After a run that ended badly - Tera Term closed, DUT rebooted mid-soak,
macro stopped by hand - the stress jobs kept running and the test session
stayed open. The next run then started on a box that was already loaded.
Nothing errored; the numbers were just quietly wrong.

Script A now opens with hw-test-session finish, bgctl reset --yes,
bgctl stop --all, then bgctl list. The list is the point of the sequence:
it is the one line in the log that proves the DUT was idle at the start.

Script A -> V1.1.1.

Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_014RetWKFZFG1ZHcitQAyhwM

docs/release-notes/v1.1.1.md

@@ -0,0 +1,42 @@
+# v1.1.1 — A run no longer inherits the last one's leftovers
+
+## 🐛 Bug fixes
+
+**A previous run's jobs and session survived into the next one**
+* Script A now clears the box before it starts: `hw-test-session finish`, `bgctl reset --yes`, `bgctl stop --all`, then `bgctl list` so you can see it came back empty.
+* This matters after a run that ended badly — a closed Tera Term window, a DUT reboot mid-soak, a macro stopped by hand. The stress jobs kept running and the session stayed open, so the next run started on a box that was already loaded. Nothing failed; the numbers were just quietly wrong, and the only hint was a `bgctl list` nobody was reading.
+* The `bgctl list` at the end is the point of the sequence, not decoration: it is the one line in the log that proves the DUT was idle when the run began.
+
+## 📦 Downloads
+
+| File | Contents |
+|---|---|
+| `Script_ABC_Blanton_V1.1.1.zip` | The full Tera Term working directory, including `Blanton_Script/` to copy onto the DUT |
+
+**After copying to the DUT:**
+
+```bash
+chmod +x ~/Blanton_Script/*.sh      # see below
+grep -rlU $'\r' ~/Blanton_Script    # expect no output
+```
+
+`blanton_ber.sh` is invoked by Script C as `./Blanton_Script/blanton_ber.sh`, so it needs the execute bit along with `bmc_monitor.sh` and `usb_target.sh` — and neither git nor a Windows/USB copy carries it reliably. Without the `chmod` the BER section fails with `Permission denied` and the log simply has no BER in it.
+
+## ⚠️ Before you run
+
+* **`hw-test-session finish` at the start will complain if no session is open.** That is expected on a fresh DUT and does not stop the run.
+* **These three tests cannot share the switch.** `blanton_ber.sh`, `blanton_tr518.sh` and `blanton_traffic_linespeed` all take over port loopback and L2 learning. Script C already orders BER after the traffic report.
+* **PRBS takes the links down** while `blanton_ber.sh` is armed. That is the test working, not a fault.
+* **`ce0` keeps running until you stop it.** If a run is interrupted between `start` and `stop`, the 100G port stays saturated with nothing in `show interfaces status` to hint at it.
+* **Two numbers must stay in step**: Script C's `sleep 30` and `blanton_ber.sh`'s `BER_INTERVAL`.
+* **`FAN_SPEED` is 100** — the fans run flat out unless you change `config.ttl`.
+* **Declare the switch population** with `SWB_UNIT0` / `SWB_UNIT1`.
+* **PRBS on the two 100G uplinks (`port_prbs_monitor.sh`) is still not wired into the macros.**
+* **The three items listed as unverified in v1.1.0 are still unverified**: the `ce0` ingress mirror, the 120s settle in `blanton_tr518.sh`, and `test mode nr=no` on stop. See [v1.1.0](https://etgit.et-wen.com/etwen/Blanton_TTL_Script/releases/tag/V1.1.0) for the one-command check on each.
+
+## 🔗 Links
+
+* [ARCHITECTURE.md](https://etgit.et-wen.com/etwen/Blanton_TTL_Script/src/branch/main/ARCHITECTURE.md) — test flow, data models, constraints
+* [CLAUDE.md](https://etgit.et-wen.com/etwen/Blanton_TTL_Script/src/branch/main/CLAUDE.md) — commands and the bench gotchas
+
+**Full changelog:** [V1.1.0...V1.1.1](https://etgit.et-wen.com/etwen/Blanton_TTL_Script/compare/V1.1.0...V1.1.1)