fix: avoid bash backslash mangling of github.action_path on Windows (fixes #150)

[adityachilka1]

Fixes #150.

The bug

When the action runs on a Windows runner, ${{ github.action_path }} resolves to a backslash-separated path like:

D:\a\_actions\modelcontextprotocol\conformance\v0.1.14

GitHub Actions then inlines that string directly into the body of the bash run: block. Bash sees \a, \m, \c, etc. as escape sequences (or as ambiguous characters whose backslashes get consumed depending on the surrounding context), and the resulting path is mangled.

That matches the symptom in #150 exactly — the error reports a lookup at:

D:\a\webman-mcp\webman-mcp\a_actionsmodelcontextprotocolconformancev0.1.14\dist\index.js

The literal \a, \_, \m, etc. were consumed during bash's processing of the inlined string, and the residue was treated as a relative path appended to the workflow's CWD (D:\a\webman-mcp\webman-mcp\).

The fix

Replace the two ${{ github.action_path }} usages inside bash run: blocks with the auto-injected $GITHUB_ACTION_PATH environment variable. GitHub Actions sets this variable on every composite-action step automatically. Because bash evaluates $GITHUB_ACTION_PATH as a variable expansion (not a template inlining), the value is treated as an opaque string — no escape processing on the backslashes.

Two-line diff:

-        cd "${{ github.action_path }}"
+        cd "$GITHUB_ACTION_PATH"
-        CONFORMANCE="${{ github.action_path }}/dist/index.js"
+        CONFORMANCE="$GITHUB_ACTION_PATH/dist/index.js"

The ${{ inputs.* }} references elsewhere in the file are kept as-is — inputs are typed strings from the workflow and don't carry Windows path separators.

Why this is the right fix (vs. alternatives)

• sed 's|\\\\|/|g' — converts backslashes to forward slashes at runtime. Works on Windows bash, but adds a runtime step and obscures the cause.
• env: ACTION_PATH: ${{ github.action_path }} — explicit env block, also works. Equivalent to using $GITHUB_ACTION_PATH but more verbose and duplicates what GHA already provides.
• $GITHUB_ACTION_PATH directly — minimal, idiomatic, matches what other composite actions in the ecosystem use (e.g., actions/setup-node, pnpm/action-setup). Picked this.

Verification

The fix can be verified by re-running the user's workflow at https://github.com/luoyue712/webman-mcp/actions/runs/22035652643 (linked in #150) with this action ref. Locally I confirmed the env-var form preserves Windows-style paths through bash variable expansion (no backslash consumption).

No behavioural change on Linux/macOS runners — $GITHUB_ACTION_PATH resolves identically to ${{ github.action_path }} on those platforms.