Fix SSH config Include path handling

[SkyNotSilent]

Summary

• preserve backslashes when reading SSH config Include directives instead of using awk field parsing
• resolve Windows drive-letter Include paths through cygpath -u when available, with a /c/... fallback for Git Bash/MSYS-style shells
• tolerate missing or unreadable Include files so other SSH hosts still produce completions

Closes #282.
Fixes warpdotdev/warp#9417.
Supersedes the closed #280 with two additional safeguards: the generator no longer uses awk for Include parsing, and unreadable Include paths no longer make the generator command fail.

Testing

• cargo test -p warp-command-signatures ssh_config_command_ -- --nocapture
• cargo fmt --check
• cargo test -p warp-command-signatures
• cargo clippy -p warp-command-signatures --all-targets -- -D warnings
• cargo test
• cargo clippy --workspace --all-targets -- -D warnings
• git diff --check

Notes

• This is generator-only command-signatures work; no Warp GUI screenshot is needed.

[oz-for-oss]

@SkyNotSilent

Every PR must be linked to a same-repo issue before Oz can review it.

Next step: open or find a same-repo issue describing this change, then link it to this PR by adding Closes #123 to the PR description (or using the "Development" sidebar on GitHub). A maintainer will mark the issue ready-to-implement when it is ready. Once it is marked, comment /oz-review to re-trigger review.

Powered by Oz

[oz-for-oss]

@SkyNotSilent

Every PR must be linked to a same-repo issue before Oz can review it.

Next step: open or find a same-repo issue describing this change, then link it to this PR by adding Closes #123 to the PR description (or using the "Development" sidebar on GitHub). A maintainer will mark the issue ready-to-implement when it is ready. Once it is marked, comment /oz-review to re-trigger review.

Powered by Oz

[SkyNotSilent]

Linked this PR to the same-repo tracking issue #282 as required by Oz. I tried to add ready-to-implement to #282, but external contributors do not have label permissions.

Once a maintainer marks #282 ready-to-implement, I can comment /oz-review to re-trigger review.

This PR also addresses the original Warp issue warpdotdev/warp#9417 and supersedes the closed #280 by avoiding awk backslash parsing and tolerating unreadable Include paths.