feat(lefthook): pick bun or pnpm from the lockfile in the shared site hooks

[taraxvoid]

The shared site hooks hardcoded bun run --if-present, which blocks the pnpm sites (rvnflt, voidsite) from adopting them. A top-level lefthook templates: entry pm resolves to pnpm when the repo has a pnpm-lock.yaml, else bun, and every command uses {pm} run --if-present. The install hints use {pm} install too.

Also fixes the header comment (ref is a tag or branch, not a SHA).

Tested as a file:// remote in throwaway repos: the bun repo runs bun run for each step, the pnpm repo (with a stub pnpm on PATH) runs pnpm run --if-present for each step. lefthook validate passes and the unit test now asserts the lockfile detection and that no bun run remains.

Note: bun run --if-present audit falls through to macOS's /usr/sbin/audit when a site defines no audit script. Pre-existing and harmless for sites that define one.

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