fix(shared,tests): bound the book contract and close the gaps that hid all this

Book page setup and element geometry were unbounded numbers, so a shared
book could be saved with zero, negative or astronomical dimensions and every
consumer downstream - the canvas, the PDF export - had to cope. Day-note caps
had drifted from the limits their own doc comment states, and icon had none.

On the test side: the path filter meant a PR touching only the root lockfile
ran no jobs at all, which is exactly the change class most likely to break a
native binding; the canAccessTrip mock is hand-copied into 72 files and had
already drifted from the real query; the path-traversal test asserted only
status !== 200, so a 500 from a broken guard passed it; and one unit test
shelled out to a real kitinerary binary if the host happened to have one.

.github/workflows/test.yml

@@ -11,6 +11,13 @@ on:
       - 'client/**'
       - 'shared/**'
       - 'plugin-sdk/**'
+      # npm workspaces hoist every dependency into the single root lockfile, so
+      # a dependency bump touches none of the four directories above — and a
+      # native binding like better-sqlite3 is exactly what needs the suite.
+      - 'package.json'
+      - 'package-lock.json'
+      - 'Dockerfile'
+      - 'docker-compose.yml'
       - '.github/workflows/test.yml'
 
 jobs: