Add try_count

[Iizuki]

Summary

Adding try_count stream terminator.

It counts the elements in a stream of results, or returns early if it finds an error.

Design

I just used the existing TryStream trait as the bound as it's nice and concise. I'm not aware of any downsides compared to specifying the bound more verbosely in terms of plain Stream.

Misc

Added crate categories to Cargo.toml. Might help a little with discoverability.

Also run cargo fmt which made u bunch of small changes here and there.

Issue refs

closes: #6

[Copilot]

Pull request overview

Adds a new StreamTools::try_count() terminator to count Ok items in a TryStream while short-circuiting on the first Err, alongside a version bump + changelog entry and some cargo fmt import/semicolon cleanups.

Changes:

• Introduce try_count via a new TryCount future and a StreamTools extension method.
• Bump crate version to 0.7.7, add crates.io categories, and update CHANGELOG.md.
• Apply formatting/import-order adjustments across several modules.

Reviewed changes

Copilot reviewed 11 out of 11 changed files in this pull request and generated 4 comments.

Show a summary per file

File	Description
src/try_count.rs	New TryCount future implementing the short-circuiting count logic.
src/lib.rs	Wires try_count into StreamTools and adds the new module.
src/throttle_last.rs	Formatting/import-order and missing semicolon fix.
src/test_util/delay_items.rs	Import order formatting.
src/sample.rs	Formatting/import-order and semicolon fix.
src/merge_join_by.rs	Import order formatting.
src/flatten_switch.rs	Import order formatting.
src/fast_forward.rs	Import order formatting and semicolon fix.
build.rs	Import order formatting.
Cargo.toml	Version bump to 0.7.7 and add crate categories.
CHANGELOG.md	Add 0.7.7 entry noting try_count.

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