chore(deps): support strum 0.28

[joshka]

Summary

This PR fixes the strum 0.28 dependency bump proposed in #210 and adds explicit cargo check --all-targets --all-features --workspace coverage so example-target compile failures are caught directly in CI instead of being missed by the existing workspace check.

Root Cause

The failure came from the tui-bar-graph example, where clap derives a parser for BarStyle.

BarStyle still derives FromStr, and this was not caused by the #[strum(default)] behavior change from strum PR #476. The actual issue was dependency resolution plus feature unification.

Before the bump, tui-bar-graph and ratatui-core both used strum 0.27, so Cargo unified them and ratatui-core's strum/std activation effectively carried std into the strum instance used by tui-bar-graph. After #210, tui-bar-graph used strum 0.28 while ratatui-core still used strum 0.27, so the graph split into separate strum packages.

At that point, tui-bar-graph's own strum 0.28 was built with default-features = false, which meant strum::ParseError no longer implemented std::error::Error in that context. That was enough to break clap's inferred parser for BarStyle.

Code Changes

tui-bar-graph now declares an explicit std feature and uses it to enable strum/std. std remains enabled by default, so the crate's normal ergonomics do not change.

The interactive example is marked with required-features = ["std"] so its compile requirements are explicit instead of depending on accidental transitive feature behavior.

colorgrad now uses default-features = false.

Why Only strum/std

strum/std matters here because it affects trait-based downstream integration on a public enum type. BarStyle derives traits whose interaction with clap depends on the trait set of strum::ParseError.

colorgrad/std does not play the same role in this crate today, so the std feature does not forward colorgrad/std.

Docs

The crate now uses document-features so the feature contract is rendered in generated docs and on docs.rs.

CI

The issue exposed by #210 was a normal compile failure in a non-lib target.

The workspace already ran cargo check --all-features --workspace, but that does not compile examples and other non-lib targets. cargo check --all-targets --all-features --workspace reproduces the failure directly.

This PR adds explicit all-targets compile coverage so example-target breakage is caught as a normal build/check failure.

Verification

cargo check --all-targets --all-features --workspace
cargo clippy --all-targets --all-features --workspace -- -D warnings
cargo check -p tui-bar-graph --lib --no-default-features
cargo doc -p tui-bar-graph --all-features
cargo rdme --check --manifest-path tui-bar-graph/Cargo.toml

Follow-up

A broader no_std audit of the other widget crates was done during this work and recorded separately on #102.

[codecov-commenter]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 87.06%. Comparing base (7596dd3) to head (10c2d76).

Additional details and impacted files

@@           Coverage Diff           @@
##             main     #224   +/-   ##
=======================================
  Coverage   87.06%   87.06%           
=======================================
  Files          22       22           
  Lines        4150     4150           
=======================================
  Hits         3613     3613           
  Misses        537      537           

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[joshka]

Updating the PR body headings to normal Markdown (##) as requested.