chore(meta): install pql replication hooks and cover the format marker

This repo had no .pql/hooks/ at all — the four replication hooks were
never installed, because pql's installer used to ignore a redirected
core.hooksPath. It works with .config/hooks now, so init prepends a
two-line shim to each hook that sources the pql half. Existing hook
bodies are untouched; the shim goes above them.

What this buys: post-merge now runs `pql plan upgrade`, so a pull that
brings in a newer changelog format migrates it forward automatically
instead of replaying under superseded rules.

.gitattributes gains a rule for changelog files at the root of
.pql/changelog/. The existing `**/*.sql` pattern requires a directory
component and so did not match the new 0000-format.sql marker, which
would have made it a merge conflict rather than a union merge.

Note for a follow-up: the hand-folded pql block in .config/hooks/post-merge
(lines ~10-12) is now redundant with the shim, so plan import and
decisions sync each run twice per pull. Both are idempotent, so this is
waste rather than breakage — but that block and its stale "installer is
dead" comment can be dropped.

Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>

.gitattributes

@@ -1 +1,2 @@
 .pql/changelog/**/*.sql merge=union
+.pql/changelog/*.sql merge=union