♻️ Run doc tests outside the coverage gate

An example that exercises a line no hand-written test reaches would let
the `--100` gate pass on documentation alone. Node has no file-level
exclusion, and c8's `--exclude` only filters the report, so run the two
in separate processes: `test:coverage` runs c8 over the tracked tests
only (`git ls-files`, which skips the untracked generated files), and
`test:doc` runs the generated examples without c8. `test:ci` chains
them.

development/docs.md

@@ -49,3 +49,9 @@ Compile every `ts / `typescript fence in the prose docs into a real
   out of the `--100` gate. Do not add an `--exclude` for them: passing any
   `--exclude` replaces the defaults, so every hand-written test file and
   `__tests__/` helper re-enters coverage and the gate fails.
+- Generated examples must not run under `c8`: an example could cover a line no
+  hand-written test reaches, so the coverage gate would pass on documentation
+  alone. `test:coverage` therefore runs c8 over the tracked tests only
+  (`git ls-files 'src/*.test.ts'` — the generated files are untracked), and
+  `test:doc` runs the examples in a separate process without c8. `test:ci`
+  chains the two, so correctness and coverage stay independent.