* Add clap-mangen to cargo-orthohelp migration guide

Document how ortho-config users can migrate manual page generation\nfrom build.rs-based clap_mangen usage to cargo-orthohelp.\n\nThe guide uses the netsuke build.rs pattern as the baseline and\ncovers dependency cleanup, metadata setup, CI/package command\nexamples, output-path updates, and migration verification steps.

* Fix migration docs review feedback

Apply requested documentation review fixes across migration notes\nand the clap-mangen to cargo-orthohelp guide.\n\n- Rename the guide file to match tool naming conventions.\n- Remove second-person phrasing in v0.8.0 migration bullets.\n- Switch 'artifacts' to en-GB 'artefacts'.\n- Clarify Rust 1.88 requirement as matching workspace rust-version.\n- Expand intermediate representation (IR) acronym on first use.

* Apply verified docs comment fixes

Verify inline review findings against current content and apply only\nneeded updates.\n\n- Change localisation -> localization in the migration guide.\n- Align packaging-path sentence to impersonal phrasing (a packaging job).\n- Rename test_helpers heading to sentence case: Intended usage.\n\nNo other reviewed items were changed because they were already compliant.

* Restore README second-person migration wording

Revert the earlier neutral-language rewrite in README migration notes.\nREADME files are allowed to use first/second-person guidance, so the\nv0.8 and v0.7 note bullets now use the prior reader-directed phrasing\nagain in both runtime and macro READMEs.

* Standardize compose_layers ellipsis notation

Verify the README finding and update documentation function references\nfrom two-dot notation to Rust-style three-dot notation.\n\n- compose_layers_from_iter(..) -> compose_layers_from_iter(...)\n- Applied across Markdown docs where this form appeared.