style: sentence-case the verbose "Template variables:" label

[max-sixty]

The three call sites that print the -v template-variable table used a lowercase template variables: — the only user-facing message in the codebase that broke the sentence-case convention for a reason other than a literal identifier keeping its real case (gh, pre-merge, a branch or repo name). Sibling messages for the same concept were already capitalized: wt step eval prints "Available template variables" and template expansion prints "Available variables:".

Capitalizes the three emitters (alias.rs, hooks.rs, command_executor.rs), the doc comments and wt hook help text that name the block, the generated hook.md mirrors, and the seven affected snapshots.

This was written by Claude Code on behalf of max

[max-sixty]

Closing — obsoleted by #3495, which already renamed these headers to {owner} template variables: (e.g. ○ greet template variables:, ○ pre-merge template variables:). Under that form the label is a lowercase continuation after an interpolated, lowercase-by-nature owner name, so capitalizing it to Template would be grammatically wrong and would re-split the family #3495 deliberately unified (it also lowercased eval's header for the same reason). This branch was based on a stale local main that predated #3495.

This was written by Claude Code on behalf of max