Align path handling with webpack, especially Windows paths

[hardfist]

Align Rust path utilities and resolver behavior with webpack. Baseline: Rspack f03bd2f4f3, webpack 5.110.3, enhanced-resolve 5.24.5, Node.js 24.16.0.

Area	Input	Rspack Rust	webpack / Node.js
Windows identifier on macOS	Context C:\project, resource C:\project\src\a.js	../C:/project/src/a.js	./src/a.js
Cross-drive identifier on macOS	Context C:\project, resource D:\lib\a.js	../D:/lib/a.js	D:\lib\a.js
make_paths_absolute	Context /workspace/app, request ../a.js	/workspace/app/../a.js	/workspace/a.js
node_join_win32 vs path.win32.join	C:\project + ../src/a.js	C:\project\../src/a.js	C:\src\a.js
Resolver classification on POSIX hosts	C:\project\a.js	Native path components classify it as a normal/bare request	enhanced-resolve classifies it as Windows absolute
Windows resolve.restrictions	Rule C:\APP, candidate C:\app\a.js	Directory comparison rejects the case difference	enhanced-resolve accepts it

The first four rows were reproduced with helper-level probes on macOS. The last two are source-level comparisons; resolver end-to-end behavior and Windows integration still need verification. Rspack's JS identifier helpers matched webpack in the sampled cases. Explicit Windows normalization and join followed by normalization also matched Node.

Implementation tasks:

• Normalize make_paths_absolute like path.join, including source-map module-identifier lookup.
• Align Windows identifier conversion across hosts and audit resolver classification.
• Align resolve.restrictions with enhanced-resolve's Windows case handling.
• Clarify node_join semantics and normalize call sites requiring Node's join behavior, especially asset output and source-map paths.

Prioritize normalization and restrictions. Reuse existing JS integration suites to cover drive letters, mixed separators, UNC paths, ./.., and case differences. UNC paths remaining unchanged in absoluteToRequest are shared webpack behavior, not a Rspack-specific gap.

[intellild]

I’d vote for URLs as a unified, cross-platform internal representation, with native path conversion only at external boundaries.

Area	Input	Internal URL input	Expected output
Windows identifier on macOS	Context C:\project, resource C:\project\src\a.js	Context file:///C:/project/, resource file:///C:/project/src/a.js	./src/a.js
Cross-drive identifier on macOS	Context C:\project, resource D:\lib\a.js	Context file:///C:/project/, resource file:///D:/lib/a.js	file:///D:/lib/a.js internally; D:\lib\a.js at the compatibility boundary
make_paths_absolute	Context /workspace/app, request ../a.js	Context file:///workspace/app/, request ../a.js	file:///workspace/a.js
Windows join	Context C:\project, request ../src/a.js	Context file:///C:/project/, request ../src/a.js	file:///C:/src/a.js
Resolver classification on POSIX	C:\project\a.js	file:///C:/project/a.js	Absolute file resource on every host
Windows resolve.restrictions	Rule C:\APP, candidate C:\app\a.js	Rule file:///C:/APP/, candidate file:///C:/app/a.js	Accept under the required Windows case-comparison rules

The representation would be consistent across platforms; filesystem-specific comparison rules would still need explicit handling.