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/JOURNAL.md

@@ -0,0 +1,14 @@
+# Project journal
+
+Append-only, newest first. **Entries are never edited** — the value of this file is
+that it records what was believed at the time, including the parts that turned out
+wrong. Where things stand *today* is in `STATUS.md`, which is generated.
+
+Four lines per entry. The analysis belongs in the issue or the decision record; this
+file carries the reasoning and the pointers.
+
+- **Why** — the driver. The one line git cannot reconstruct later.
+- **Obligates** — issues this change created elsewhere. Numbers, not prose.
+- **Refs** — commits, issues, decision records.
+
+---