fix(system/os/windows): pin every ext import to its providing DLL

[octalide]

Closes #334.

What

Every ext fun under src/system/os/windows/ and the windows runtime entrypoint (src/runtime/windows/x86_64.mach) now carries an explicit #[library] decorator naming its providing DLL. Previously the ~61 kernel32 imports were unattributed: they reached the PE writer as DYNLIB_ANY and relied on the COFF fallback binding them to dependency 0, which is correct only while kernel32.dll happens to sort first. The first mixed-DLL consumer (e.g. one also linking glfw3.dll) breaks that implicit ordering contract, mis-binding a whole DLL set and producing STATUS_ENTRYPOINT_NOT_FOUND at load.

The change is purely additive — links that were already ordered correctly are unchanged — and removes the implicit ordering dependency entirely.

Sweep

Exhaustive grep across the windows + runtime trees: 78 ext fun total. 17 were already pinned (14 ws2_32, 2 synch-apiset, 1 advapi32). The remaining 61 kernel32 imports are now pinned. A grep for any ext fun not immediately preceded by a #[library decorator comes back empty.

Obsolete comments documenting the old first-dependency reliance (header, CreateSymbolicLinkA, runtime entrypoint) were updated to match.

Verification

• mach build . + mach test .: 620 passed, 0 failed (native linux/x86_64).
• Cross-build for windows-x86_64: succeeds; every windows os/runtime module compiles.
• Import-directory proof (acceptance Convert all method declarations to C-style prefixed free functions #3). Built a consumer PE with kernel32.dll deliberately placed last in libs (dependency index 3, not 0) and dumped the import directory: all 53 referenced kernel32 imports resolve under kernel32.dll, 14 under ws2_32.dll, 1 under advapi32.dll, 2 under the synch apiset — each attributed to the correct DLL despite the adverse ordering.
• Falsifiability. Removing a single pin (WriteFile) and rebuilding the same PE re-binds WriteFile to ws2_32.dll (dependency 0) — the exact mis-bind the issue describes. Restoring the pin returns it to kernel32.dll.