fix(npm): normalize CLI bin path

[obmakesomething]

What changed

• Normalizes the npm bin.env-mapper path from ./src/cli.js to src/cli.js using npm pkg fix.

Why

npm publish --dry-run --access public warned that npm would auto-correct and remove the bin entry when publishing. That would risk publishing env-mapper-mcp@0.1.0 without the env-mapper CLI.

Validation

• npm run prepublishOnly passes.
• npm publish --dry-run --access public passes without the bin auto-correction warning.

Non-goals

• No npm publish in this PR.
• No version bump.
• No runtime behavior changes.

[devloai]

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