[codex] Remove unused Rust helpers (#17146)

## Summary

Removes high-confidence unused Rust helper functions and exports across
`codex-tui`, `codex-shell-command`, and utility crates.

The cleanup includes dead TUI helper methods, unused
path/string/elapsed/fuzzy-match utilities, an unused Windows PowerShell
lookup helper, and the unused terminal palette version counter. This
keeps the remaining public surface smaller without changing behavior.

## Validation

- `just fmt`
- `cargo test -p codex-tui -p codex-shell-command -p codex-utils-elapsed
-p codex-utils-fuzzy-match -p codex-utils-string -p codex-utils-path`
- `just fix -p codex-tui -p codex-shell-command -p codex-utils-elapsed
-p codex-utils-fuzzy-match -p codex-utils-string -p codex-utils-path`
- `git diff --check`

codex-rs/utils/fuzzy-match/src/lib.rs

@@ -68,15 +68,6 @@ pub fn fuzzy_match(haystack: &str, needle: &str) -> Option<(Vec<usize>, i32)> {
     Some((result_orig_indices, score))
 }
 
-/// Convenience wrapper to get only the indices for a fuzzy match.
-pub fn fuzzy_indices(haystack: &str, needle: &str) -> Option<Vec<usize>> {
-    fuzzy_match(haystack, needle).map(|(mut idx, _)| {
-        idx.sort_unstable();
-        idx.dedup();
-        idx
-    })
-}
-
 #[cfg(test)]
 mod tests {
     use super::*;