Show a size that rounds up to 1024 in the next unit

[kevin9327]

human_bytes only steps up a unit at 1024, but from 9.95 up it prints no decimal. So any size between 1023.5 and 1024 of a unit is shown as 1024 of that unit:

bytes	before	after
1,048,575	1024 KiB	1.0 MiB
1,073,741,823	1024 MiB	1.0 GiB
1,047,552 (1023 KiB)	1023 KiB	1023 KiB

human_count has the same problem at 1000: 999,999 files is shown as 1000.0k, and 999,999,999 as 1000.0M. Both now step up where the displayed number would round to the next unit (1023.5 for bytes, 999,950 and 999,950,000 for counts). The labels on tiles, the header and the review list all go through these two functions.

How I verified it:

• New test a_value_that_rounds_up_to_the_next_unit_is_shown_in_it in size.rs. It fails on main (left: "1024 KiB", right: "1.0 MiB") and passes with this change. The existing size tests still pass.
• cargo fmt --all --check and cargo clippy --all-targets -- -D warnings on disktree-core (toolchain 1.97): clean.
• cargo test in disktree-core: 130 passed. Three removal trash tests fail the same way on unmodified main in my sandbox ("on a different filesystem than the trash"), so they aren't related to this change.
• I didn't build disktree-app (no GPUI system libraries here). It only calls these functions; there's no signature change.

[chatgpt-codex-connector]

You have reached your Codex usage limits for code reviews. You can see your limits in the Codex usage dashboard.