node_runtime: Bound managed npm cache growth

[AlisinaDevelo]

Objective

• Fixes Managed npm cache (node/cache) grows unbounded, never pruned #59409.
• Prevent Zed's npm cache from accumulating a new dependency tree and retained tarballs whenever a registry agent version changes.

Solution

• Install registry npm agents into their existing stable per-agent prefixes, replacing the previous version in place.
• Resolve and execute the installed package binary using npm's binary-selection rules.
• Use a temporary download cache when an agent package changes, while reusing unchanged installations without invoking npm.
• Remove legacy _npx and _cacache directories once, preserving unrelated cache contents such as npm logs.

Testing

• cargo test -p node_runtime (23 tests passed)
• cargo check -p project
• cargo clippy -p node_runtime --all-targets -- -D warnings
• cargo clippy -p project -- -D warnings
• On macOS, upgraded an agent-style bounded npm package from 7.7.1 to 7.7.2 in the stable prefix and confirmed that npm created zero _npx environments.

Linux and Windows were not manually tested.

Self-Review Checklist:

• I've reviewed my own diff for quality, security, and reliability
• Unsafe blocks (if any) have justifying comments
• The content adheres to Zed's UI standards (no UI changes)
• Tests cover the new/changed behavior
• Performance impact has been considered and is acceptable

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Release Notes:

• Fixed unbounded npm cache growth caused by registry agent package updates.

[AlisinaDevelo]

Hey, just checking in on the npm cache change—does this need anything else from me to move forward?

[huzaif-fahad]

Hey @AlisinaDevelo #61750 I think this PR fixed this issue, I am not sure as I am not a rust dev. Just for your info ^

[SomeoneToIgnore]

Sorry: apparently, the PR was overlooked as never left the draft status and, as mentioned, another one was created to fix the issue.

Will close this one as the fix is merged now.