docs: list termlens-cli in AGENTS.md's layout

[cestercian]

What & why

AGENTS.md is the file coding agents read first. Its Layout section listed the library, fixtures/ and docs/DESIGN.md but not crates/termlens-cli/, so an agent changing termlens inspect or termlens render was not told where that code lives. This adds a bullet in the same style as the library's, and notes that examples/inspect.rs mirrors termlens inspect and tests/inspect.rs checks that the two agree. Docs only.

Closes #538

Checklist

• Linked an issue (or explained above why none exists)
• Tests added/updated for the change: n/a, one bullet
• cargo fmt --all and cargo clippy --workspace --all-targets --all-features are clean: no Rust changes
• All commits are signed off (git commit -s)
• No AI attribution trailers
• CHANGELOG.md updated under [Unreleased] (user-facing changes only): n/a, docs only
• Snapshot changes (if any) were reviewed with cargo insta review, not blind-accepted: n/a

.github/scripts/check-readme-links.sh passes on the edited files.

[vyncint]

Thanks! I checked the bullet against the tree: both paths exist, the three subcommands are the CLI's real ones, it is published as termlens-cli, and tests/inspect.rs does check that the example and the command agree (six parity tests), so "a change to one needs the other" is accurate. The wrapping matches its neighbours.

CI was red on this PR for reasons unrelated to your change (an upstream action's moving v1 tag tripped the zizmor audit; fixed on main in #554). I updated your branch with it, so the re-run is all green. Merging.