feat: move script parsing to vite_shell and add source spans

[branchseer]

TL;DR

Migrate shell parsing functionality from vite_task to a dedicated vite_shell crate, improving shell command parsing with better location tracking.

What changed?

• Moved TaskParsedCommand and shell parsing logic from vite_task/cmd.rs to the vite_shell crate
• Enhanced the shell parser to track source locations of commands in addition to parsing them
• Updated try_parse_as_and_list to return both parsed commands and their source ranges
• Updated the workspace to use the new shell parsing functionality
• Pinned to a specific git revision of brush-parser to fix a bug with AST node locations

[branchseer]

• feat: move script parsing to vite_shell and add source spans #55 👈 (View in Graphite)
• main

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