feat: select issue form when logging

[emmajam]

Adds a local --template override to frog log, allowing a repository to select a purpose-specific issue form while retaining Frog's existing labels and lifecycle.

• Resolves filenames under .github/ISSUE_TEMPLATE and repository-relative paths through the existing form lookup.
• Gives the explicit flag precedence over configured and discovered forms.
• Rejects the local-only option for upstream targets and non-file stores.
• Documents the workflow and adds regression coverage.
• pnpm check and an end-to-end CLI smoke test pass. The focused Vitest suite could not collect without a Docker-compatible container runtime; the included friction entry records that blocker.

CLOSES #80

[vercel]

@emmajam is attempting to deploy a commit to the Wevm Team on Vercel.

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