feat: add Windows x64 support

[Paul-Yuchao-Dong]

This PR adds native Windows x64 (x86_64-pc-windows-msvc) support to postagent.

Changes

• New platform package postagent-win32-x64 — publishes a native Windows binary via npm, following the same optional-dependency pattern as the existing darwin/linux packages.
• Binary resolution — bin-resolve.ts and postinstall.cjs now map win32-x64 to postagent-win32-x64, using .exe extension on Windows. chmod errors on Windows are caught (it's a no-op there).
• CI matrix — Added x86_64-pc-windows-msvc target running on windows-latest to the publish workflow, and included the win32-x64 package in the publish loop.
• Documentation — Updated README with platform support table and a build-from-source guide for Windows users who need to compile the Rust binary locally.

Testing

Tested on Windows 11 x64 with Node.js — postagent CLI resolves the native binary correctly, postinstall runs without errors, and the .exe extension is handled properly.

Fixes # (no existing issue — new platform target)

[4bmis]

@codex review

[chatgpt-codex-connector]

💡 Codex Review

postagent/packages/postagent/package.json

Line 37 in 63914da

"postagent-win32-x64": "workspace:*"

Commit the lockfile update for the Windows package

This adds a new workspace optionalDependency, but pnpm-lock.yaml still lists only the existing four platform packages under packages/postagent. The release workflow runs pnpm install --frozen-lockfile, and the publish workflow runs pnpm install on GitHub Actions where pnpm defaults frozen lockfile to true in CI (pnpm docs), so the next release/publish install will fail as soon as it checks the out-of-sync manifest. Please regenerate and commit the lockfile entry for postagent-win32-x64.

---

postagent/packages/postagent-win32-x64/package.json

Lines 2 to 3 in 63914da

	"name": "postagent-win32-x64",
	"version": "0.3.2",

Add the Windows package to the fixed version group

This introduces a sixth npm package, but .changeset/config.json still fixes only postagent plus the four existing platform packages, so pnpm version-packages will not bump postagent-win32-x64 with the rest of the release. After the first release, postagent can point Windows users at an older native binary package, violating the repo's version-lockstep rule and risking CLI/core mismatches. Add this package to the fixed group (and include it in the release changeset) before publishing.

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postagent/README.md

Line 35 in 63914da

npm install -g .

Point the source install command at the CLI package

Running this from the repository root does not install the CLI: the root package.json is a private workspace root with no name, version, or bin, and npm pack --dry-run . from that directory fails with Invalid package, must have name and version. Windows users following the fallback instructions will not get a postagent command; the global install step needs to target the actual CLI package/workspace after building the binary.

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[4bmis]

Hi @Paul-Yuchao-Dong , thanks for contribution! But there are some issues in this PR, please fix them.