report all files in CI test coverage (#10560)

refs: #10559

## Description

#10556 made coverage reports include all files, but only in package reports. This makes CI's report across all packages also use `--all`.

While working on this I wanted to be able to document all the kinks I ran into so I also consolidated this capability in a single script with explanatory comments. 

### Security Considerations
none

### Scaling Considerations
none

### Documentation Considerations
includes docs now

### Testing Considerations
The `coverage` job  runs in the after-merge workflow but only on `push` so I can't trigger it in CI. Instead I've run the script locally. When it reaches cosmic-swingset it dies on `./bin/rosetta-cli` but I just skipped that package and confirmed the generated report is as expected.

### Upgrade Considerations
n/a

.github/workflows/after-merge.yml

@@ -105,10 +105,8 @@ jobs:
         with:
           node-version: ${{ matrix.node-version }}
 
-      - name: generate coverage for all tests
-        run: 'yarn test:c8-all || :'
-      - name: generate coverage/html reports
-        run: mkdir -p coverage/tmp && yarn c8 report --reporter=html-spa --reports-dir=coverage/html --temp-directory=coverage/tmp
+      - name: generate test coverage report
+        run: ./scripts/ci/generage-test-coverage-report.sh
       - uses: actions/upload-artifact@v4
         with:
           name: coverage

COVERAGE.md

@@ -12,10 +12,7 @@ source-to-source transforms (such as `@endo/bundle-source`,
 Coverage reports for the current main branch are
 published by CI to: https://agoric-sdk-coverage.netlify.app
 
-It's made by a CI job calling `test:c8-all` in the project root. That in turn
-calls `test:c8` in each package, with `$C8_OPTIONS` set to a common coverage
-directory and to leave temp files so they can accumulate. The job then uses that
-output in another call to c8 to generate a report.
+See `scripts/ci/generate-test-coverage-report.sh`
 
 ## Per package
 You can create a report in any package:

package.json

@@ -65,7 +65,6 @@
     "lint": "run-s --continue-on-error lint:*",
     "lint:packages": "yarn lerna run --no-bail lint",
     "test": "yarn lerna run --no-bail test",
-    "test:c8-all": "rm -rf coverage/tmp && C8_OPTIONS=\"--clean=false --temp-directory=$PWD/coverage/tmp\" lerna run test:c8",
     "test:xs": "yarn workspaces run test:xs",
     "build": "yarn workspaces run build && scripts/agd-builder.sh stamp yarn-built",
     "postinstall": "patch-package && scripts/agd-builder.sh stamp yarn-installed",

scripts/ci/generate-test-coverage-report.sh

@@ -0,0 +1,17 @@
+#!/bin/bash
+
+# CI artifact export expects the files to be under `coverage` (same for /html below)
+export NODE_V8_COVERAGE="$PWD/coverage/tmp"
+
+# clear out old coverage. c8 usually does this but we have to clean=false below so it accumulates across packages
+rm -rf "$NODE_V8_COVERAGE"
+mkdir -p "$NODE_V8_COVERAGE"
+
+# the package test:c8 commands will include this
+export C8_OPTIONS="--clean=false"
+
+# XXX uses lerna when `yarn workspaces run` should work, but in v1 it always bails on missing script
+yarn lerna run test:c8
+
+# report over all src and tools files, not just the ones that were loaded during tests
+yarn c8 report --all --include 'packages/*/{src,tools}' --reporter=html-spa --reports-dir=coverage/html