perf(git): drop intermediate Vec in format_command join (#4153)

[wuisabel-gif]

Closes #4153 (v0.8.68 §6.7 / B3.3 — remove collect before join allocations).

What

format_command in crates/tui/src/tools/git.rs collected args into a
Vec<&str> purely to .join(" ") it. Since args is &[String],
<[String]>::join(" ") does the same directly with no intermediate
allocation and byte-identical output.

-        args.iter()
-            .map(String::as_str)
-            .collect::<Vec<_>>()
-            .join(" ")
+        args.join(" ")

finance.rs left as-is

The issue also lists finance.rs, but its site maps
AttemptFailure::summary() which returns an owned String. There is no
Iterator::join in std, so joining requires materializing the Vec
first — the allocation is not unnecessary there. Per the acceptance
note ("where type constraints allow it"), that site is unchanged.

Verification

Output is unchanged. Verified the idiom compiles and the new expression
produces identical output to the old one:

args = ["status", "--porcelain"]
new: args.join(" ")                                   == "status --porcelain"
old: args.iter().map(as_str).collect::<Vec<_>>().join(" ") == "status --porcelain"

[github-actions]

Thanks @wuisabel-gif for taking the time to contribute.

This repository is observing a maintainer-managed PR intake gate in dry-run mode, so this pull request is staying open. This note helps maintainers prepare the allowlist before any enforcement is considered.

Please read CONTRIBUTING.md for the expected contribution shape. A maintainer can grant recurring PR access by commenting /lgtm on a pull request.

[Hmbown]

Superseded by PR #4216 (merged). Issue #4153 is already closed.