[sreyassabbani]

What changes

A closed-lid session currently responds to macOS serious thermal pressure by enabling Low Power Mode and continuing to hold sleep. Add a default-on endClosedLidWhenHot setting that ends that session and restores its owned changes at serious or critical pressure. Open-lid behavior stays configurable through the existing thermal rules; users can explicitly disable the closed-lid cutoff.

Decode older configuration files with the new setting enabled. Add a Settings explanation, an end notification, and the corresponding supervised real-Mac validation item. This uses macOS thermal pressure, not a temperature sensor, and cannot establish that operation in a backpack is safe.

How it was tested

• 77 targeted configuration, floor-rule, and floor-rule driver tests passed on Apple Silicon, macOS 27.0, Xcode Swift 6.4. Regression cases cover migration defaults, serious/critical closed-lid cutoffs, the opt-out, and restoration of owned power state.
• A subsequent full suite with this change plus the dependent recovery change ran 1,259 tests: 13 tmux integration cases skipped because tmux was outside the fixed executable candidates; zero failures. This is combined-stack evidence, not an isolated installed-app test.
• Release builds with warnings treated as errors passed locally.

Real-Mac evidence

Not run: installation and supervised closed-lid power/thermal checks. The app was not installed and no live power-setting changes or process freezing were performed. The new checklist item in docs/releasing.md remains required before release, and the head-specific installed-app report required by CONTRIBUTING.md remains outstanding before merge.

Opened as a draft for acceptance and review. No merge is requested until the maintainer's checks and hardware evidence are satisfied.