Fix brightness races, display resource leaks, and DDC/build errors

[shay2000]

A brightness restore after waking could overwrite newer user input. Repeated display discovery retained resources, Intel DDC replies lost their high bytes, and failed builds could be accepted as usable app bundles.

• Cancel superseded software-brightness ramps, apply their exact endpoint on the main queue, and stop queued steps during sleep or reconfiguration. Keep semaphore permits balanced.
• Release IOKit handles, temporary buffers, and closed shade windows along their ownership paths, including optimized builds and failure exits.
• Keep I2C buffers valid throughout synchronous requests and preserve all 16 bits of Intel DDC values.
• Roll back failed EDR setup before applying an XDR gamma boost.
• Require successful compilation, an existing app bundle, and a valid final signature before reporting build success; preserve the ad-hoc signing fallback.

Validation: 22 XCTest tests passed with no reported runtime warnings, including stale-write, endpoint, cancellation, shade-deallocation, semaphore, and DDC-decoding regressions. All five build-script cases passed; the partial-output case reproduced false success before the fix. A universal Release build using Xcode 27 beta contains x86_64 and arm64 and passes deep, strict codesign verification. GitHub CI passed build/test and universal DMG jobs for c6a41c0.

Physical monitor adjustment and hot-plug behavior were not exercised. The Metal setup failure guard was reviewed and compiled, but that failure was not injected at runtime.

[greptile-apps]

Greptile Summary

This PR improves display-state correctness, resource ownership, DDC communication, and build artifact validation.

• Cancels superseded software-brightness ramps and prevents queued writes during sleep or display reconfiguration.
• Releases IOKit objects, temporary allocations, and closed shade windows along their ownership paths.
• Keeps I2C buffers alive during synchronous requests and correctly decodes 16-bit DDC values.
• Rolls back incomplete EDR setup before attempting an XDR gamma boost.
• Rejects failed, missing, or incorrectly signed build outputs and adds regression coverage in CI.

Confidence Score: 5/5

The PR appears safe to merge, with no accepted new findings or outstanding review issues provided for re-evaluation.

The current head is identical to the previous review SHA, so there are no changes since the previous review that introduce a new actionable issue; the full diff also contains no confirmed repository-rule violations.

Important Files Changed

Filename	Overview
MonitorControl/Model/Display.swift	Adds generation-based cancellation, balanced semaphore handling, main-thread ramp steps, and exact software-brightness endpoints.
MonitorControl/Support/IntelDDC.swift	Corrects I2C buffer lifetimes, preserves both bytes of DDC words, and closes IOKit ownership leaks.
MonitorControl/Support/Arm64DDC.swift	Releases traversed registry entries and temporary path storage while preserving ownership of returned entries.
MonitorControl/Support/DisplayManager.swift	Removes permanent retention of closed shade windows and explicitly controls AppKit close behavior.
MonitorControl/Support/XDREngine.swift	Stops and rolls back incomplete EDR setup before applying an XDR boost.
build/build.sh	Requires successful compilation, an existing bundle, and a valid final signature before reporting success.
build/test-build.sh	Adds isolated regression cases for partial builds, successful builds, signing fallback, missing artifacts, and invalid signatures.
.github/workflows/ci.yml	Runs build-script failure-handling regression tests in CI.

Flowchart

%%{init: {'theme': 'neutral'}}%%
flowchart TD
  A[Brightness request] --> B[Increment request generation]
  B --> C{Smooth request?}
  C -- No --> D[Apply exact value]
  C -- Yes --> E[Queue next main-thread step]
  E --> F{Current generation and system active?}
  F -- No --> G[Cancel queued ramp]
  F -- Yes --> H[Apply bounded step]
  H --> I{Target reached?}
  I -- No --> E
  I -- Yes --> J[Exact endpoint applied]

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_{Reviews (3): Last reviewed commit: "Fix stale brightness ramps and Intel DDC..." | Re-trigger Greptile}

[shay2000]

@greptileai