chore(packaging): initialise compass project tracking

Adds pm/compass.toml with five workstreams (theme, logo, quarto, helpers,
packaging), the journal and decision-record scaffold, and a composed
.roborev.toml carrying nine project-specific review rules derived from the
package's actual conventions.

Also adds AGENTS.md as the cross-tool conventions file, wires project memory
into .agent/memory/ so it travels between machines, and untracks
tests/testthat/Rplots.pdf, which churned on every test run.

pm/decisions/README.md

@@ -0,0 +1,11 @@
+# Decisions
+
+One file per decision, numbered and immutable. A decision that changes is superseded
+by a new record, never edited in place — the old reasoning is the point.
+
+The table below is **generated** by `compass:decide`. Do not hand-edit it.
+
+<!-- compass:begin decisions -->
+| # | Date | Decision | Status |
+|---|---|---|---|
+<!-- compass:end decisions -->