fix(config): use path/filepath for OS-correct path separators

[hazelmayank]

Summary

Replace the path package with path/filepath in pkg/config/localconfig.go
so the CLI builds filesystem paths with the OS-correct separator.

Fixes #441 .

Background

The Go standard library splits path manipulation across two packages:

• path — always uses /. Meant for URLs and slash-separated paths.
• path/filepath — uses the OS-specific separator. Meant for filesystem paths.

localconfig.go was using path.Join / path.Dir to construct filesystem
paths. On Windows this produced mixed-separator paths because os.UserHomeDir()
returns backslashes but path.Join then appended with forward slashes.

Changes

pkg/config/localconfig.go:

• Replaced import "path" with import "path/filepath".
• Replaced 3 path.Join calls with filepath.Join (lines 112, 133, 142).
• Replaced 2 path.Dir calls with filepath.Dir (lines 158, 410).

No other files needed changes — path was only used in this file for filesystem
path construction.

Before / After (Windows 11)

Before:

> microcks --help
      --config string   Path to Microcks config (default "C:\Users\<USER>/.config/microcks/config")
> microcks context
2026/05/27 00:35:59 No contexts defined in C:\Users\<USER>/.config/microcks/config

After:

> microcks --help
      --config string   Path to Microcks config (default "C:\Users\<USER>\.config\microcks\config")
> microcks context
2026/05/27 00:35:59 No contexts defined in C:\Users\<USER>\.config\microcks\config

Linux / macOS output is unchanged.

Test plan

• go build . succeeds on Windows.
• microcks --help shows all-backslash default config path on Windows.
• microcks context shows all-backslash path on Windows.
• CI passes on all platforms.

Related

This is in the same family as #352 / PR #353 (Windows absolute path parsing).