feat: add native Windows ARM64 support

[dakehero]

Summary

Windows ARM64 currently has no native DLL in the published package. This change builds and publishes rust_pty_arm64.dll and selects it on Windows ARM64, preserving the existing x64 filename and local-build fallback.

• statically link the MSVC runtime so the prebuilt DLL has no Visual C++ Redistributable prerequisite
• run the existing unit and integration suites against the staged ARM64 artifact on GitHub's Windows ARM64 runner
• stabilize the existing PowerShell integration test by disabling profile loading and setting an explicit timeout longer than its internal wait

This fills the remaining native dependency gap for anomalyco/opencode#45875. The OpenCode installer and Bun upgrade are being handled separately in anomalyco/opencode#44665 and anomalyco/opencode#44946.

Local verification

• Windows 11 ARM64 with Bun 1.4.2 ARM64
• PE machine type: 0xAA64
• imported libraries: Windows system DLLs only; no VCRUNTIME140.dll or UCRT runtime imports
• 86 unit tests passed
• 11 integration tests passed, 5 skipped
• PowerShell integration test passed 5 consecutive runs

Summary by CodeRabbit

• New Features
  • Added native support for Windows on ARM64, allowing the application to use a platform-specific native library on compatible systems.
  • Improved native-library selection across supported platforms and architectures, including Windows ARM64, macOS, and Linux variants.
• Bug Fixes
  • Improved the reliability of the Windows PowerShell integration test by running it in a non-interactive session with a longer timeout.

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ℹ️ Recent review info

⚙️ Run configuration

Configuration used: Organization UI

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Run ID: 3b627602-66f7-4aac-a09c-5936fb05408f

📥 Commits

Reviewing files that changed from the base of the PR and between 1777e68 and 0991796.

📒 Files selected for processing (1)

• src/terminal.integration.test.ts

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Walkthrough

The runtime selects native-library filenames by platform and architecture, including a Windows ARM64 DLL name. The publish and test workflows build the Windows ARM64 target with static CRT flags. The test workflow stages the ARM64 DLL under its platform-specific name.

Changes

Windows ARM64 support

Layer / File(s)	Summary
Native library resolution src/library.ts, src/terminal.ts, src/terminal.test.ts, src/terminal.integration.test.ts	The runtime uses libraryFilenames for platform-specific candidate names and selects rust_pty_arm64.dll for the embedded Windows ARM64 library path. Tests check Windows ARM64 and x64 filename lists. The PowerShell integration test adds process options and a 15-second timeout.
Windows ARM64 build wiring .github/workflows/publish.yml, .github/workflows/test.yml	The workflows add a Windows ARM64 build target and pass matrix-provided RUSTFLAGS to non-zigbuild builds. The test workflow stages the output as rust_pty_arm64.dll and removes the generic DLL from the release directory.

Priority: ➖ Normal

Estimated code review effort: 2 (Simple) | ~12 minutes

Change: Feature

Merge Risk: ⚪ Minimal · up to 09917

The ARM64 artifact wiring is consistent, and no actionable merge-blocking defect is established by the inspected changes.

Architecture Summary

Architecture risk: 🔵 Low · up to 09917

The change affects 1 system.

Changed systems: src

Architecture concerns
No architecture-level concerns identified.

Review details

Systems and components

• observed — src (service) was modified; 4 changed files map to changed impact.

Before / after behavior

• observed — Modified behavior in src/library.ts: Added libraryFilenames, which branches on platform (darwin/win32/other), architecture (arm64), and the musl flag to return ordered candidate library filenames: .dylib names on macOS, .dll names on Windows, and .so names on Linux, with arm64-specific and musl-specific variants included in the candidate lists.
• observed — Modified behavior in src/terminal.test.ts: Adds a describe("native library resolution") block importing libraryFilenames from ./library, with tests verifying the ARM64 DLL list is preferred on win32/arm64 and the generic rust_pty.dll name is kept on win32/x64.
• observed — Modified behavior in src/terminal.ts: Adds an import of libraryFilenames from ./library.
• observed — Modified behavior in src/terminal.ts: The embedded library path template now selects rust_pty_arm64.dll when running on win32 with arm64, instead of always using rust_pty.dll on Windows.

🚥 Pre-merge checks | ✅ 4 | ❌ 1

❌ Failed checks (1 warning)

Check name	Status	Explanation	Resolution
Docstring Coverage	⚠️ Warning	Docstring coverage is 0.00% which is insufficient. The required threshold is 80.00%. Docstring coverage is scoped to functions touched by this diff. Analyzed 2 functions across 5 files.	Write docstrings for the functions missing them to satisfy the coverage threshold.

✅ Passed checks (4 passed)

Check name	Status	Explanation
Description Check	✅ Passed	Check skipped - CodeRabbit’s high-level summary is enabled.
Title check	✅ Passed	The title clearly and concisely describes the primary change: adding native Windows ARM64 support.
Linked Issues check	✅ Passed	Check skipped because no linked issues were found for this pull request.
Out of Scope Changes check	✅ Passed	Check skipped because no linked issues were found for this pull request.

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✨ Finishing Touches

🧪 Generate unit tests (beta)

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_{I’m a rabbit with a build to cheer,
ARM64 DLLs now appear.
Names resolve by platform and kind,
Test flags keep the workflow aligned.
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Actionable comments posted: 1

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Inline comments:
In @.github/workflows/test.yml:
- Around line 73-74: Create the rust-pty/target/release staging directory before
the Copy-Item command, then guard Remove-Item so it runs only when the generic
rust_pty.dll exists.

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ℹ️ Review info

⚙️ Run configuration

Configuration used: Organization UI

Review profile: CHILL

Plan: Pro Plus

Run ID: a426a1b4-931e-4004-b306-5a6ca1f33abe

📥 Commits

Reviewing files that changed from the base of the PR and between f461926 and 4c816fc.

📒 Files selected for processing (7)

• .github/scripts/windows-arm64-compile-smoke.ts
• .github/workflows/publish.yml
• .github/workflows/test.yml
• README.md
• src/library.ts
• src/terminal.test.ts
• src/terminal.ts

Included review availability: Your plan provides up to 1 included review per hour; 0 remain after this review.

[dakehero]

@sursaone When you have a chance, could you approve the external Actions run and review this PR? It adds the missing native Windows ARM64 DLL while preserving the existing x64 filename. I validated the PE ARM64 artifact on Windows 11 ARM64 with Bun 1.4.0: 86 unit tests, 11 integration tests, and an out-of-tree bun build --compile smoke executable all passed. The ARM64 DLL also statically links the CRT, so it has no VC++ Redistributable prerequisite.

[sursaone]

@dakehero Could you please check the CI tests. Thanks

[dakehero]

I've increased the PowerShell integration test timeout. Could you please approve the latest CI run again? Thanks!

[sursaone]

@dakehero Thanks for the update. The Windows ARM64 CI job is still failing on the PowerShell integration test. Could you please check again? Thanks

[dakehero]

I've updated the PowerShell test to use a module-qualified command, avoiding the slow module discovery on the Windows ARM64 runner.

The full workflow now passes on my fork, including Windows ARM64: CI run.

Could you please approve the latest CI run again? Thanks!