#13399: Hooks: support gogcli executable fallback for Gmail

Fixes #9420 linux issue by providing an alias in the code for gog to gogcli. <!-- greptile_comment --> <h2>Greptile Overview</h2> <h3>Greptile Summary</h3> Updates the Gmail hook tooling to accept both `gog` and `gogcli` executable names. The hook setup/service paths now resolve the installed binary and use it consistently when starting/renewing the Gmail watch and when spawning the `gog gmail watch serve` process. `ensureDependency` was extended to support alternative binary names and improved error messaging on non-macOS platforms. Documentation and changelog were updated to reflect the new accepted executable names, and tests were added to validate binary resolution and Linux error messaging. <h3>Confidence Score: 5/5</h3> - This PR is safe to merge with minimal risk. - Changes are localized to Gmail hook setup/watcher logic and dependency checks; the new binary resolution is used consistently at call sites and covered by targeted unit tests. No functional regressions were identified in the changed code paths. - No files require special attention <!-- greptile_other_comments_section --> _{(2/5) Greptile learns from your feedback when you react with thumbs up/down!} **Context used:** - Context from `dashboard` - CLAUDE.md ([source](https://app.greptile.com/review/custom-context?memory=fd949e91-5c3a-4ab5-90a1-cbe184fd6ce8)) - Context from `dashboard` - AGENTS.md ([source](https://app.greptile.com/review/custom-context?memory=0d0c8278-ef8e-4d6c-ab21-f5527e322f13)) <!-- /greptile_comment -->