chore: adopt the workspace agent-config baseline

Commits a .claude/settings.json rather than leaving permissions to
per-developer local state, and initialises a pql vault for this repo's
tickets and internal decisions.

Every git deny rule appears in both the `git <verb>` and `git * <verb>`
forms. Only the second catches `git -C <path>`, and without it the whole
deny list is decorative -- it looks like a policy and stops nothing.

The allow list carries pql's absolute path alongside the bare name.
pql is installed to ~/.local/bin, which is on the login PATH but not the
one a non-interactive shell gets, so the bare-name rules match nothing on
their own and every call would prompt anyway.

.gitignore now covers .claude/settings.local.json, which is machine-local
and must never be shared. `pql init` contributed the .pql/* rules with an
exception for the changelog, which is the replication log of record and
has to be committed for tickets to travel with a clone.

Co-Authored-By: Claude <noreply@anthropic.com>

.gitattributes

@@ -0,0 +1 @@
+.pql/changelog/*.sql merge=union