transpiler cache: give the Rust line its own .pile2 filename namespace - #31803

Running Vale across on the following files affected by this PR:

- runtime/environment-variables.mdx

Attempting to initialize Vale linter...
No customer vale configuration detected. Using Mintlify's default configuration.
Attempting to run Vale spellcheck...
Vale spellcheck completed successfully.

docs/runtime/environment-variables.mdx:
	- 199:58     Did you really mean 'transpiler'?
	- 199:80     Did you really mean 'transpiled'?
	- 199:144    Did you really mean 'CLIs'?
	- 206:46     Did you really mean 'Prepends'?
	- 208:12     Did you really mean 'transpiler'?
	- 210:40     Did you really mean 'transpiled'?
	- 210:153    Did you really mean 'CLIs'?
	- 216:25     Did you really mean 'transpiler'?
	- 218:24     Did you really mean 'transpiler'?
	- 228:7      Did you really mean 'transpiled'?
	- 229:7      Did you really mean 'sourcemap'?
	- 229:25     Did you really mean 'transpiled'?


Found 12 suggested changes across 1 files in 592.80ms