codecov/project fails on unrelated PRs: coverage-report does not wait for ha-integration-tests

[lvca]

What happens

codecov/project reports a whole-project coverage drop on PRs that cannot have caused one, so the check is red on
work that never touched the affected code. On #5685 (a 29-line change confined to
engine/src/main/java/com/arcadedb/index/hash/) Codecov reported:

Files          1770     1770
Lines        150057   150086      +29
Hits         101236   100126    -1110     <-- 1,110 covered lines disappear

A 29-line change cannot delete 1,110 hits. Every one of the 34 files that lost coverage is in ha-raft/:

Hits lost	File	base -> head
-295	RaftReplicatedDatabase.java	68.16% -> 29.19%
-229	RaftHAServer.java	57.71% -> 38.07%
-116	ArcadeStateMachine.java	66.66% -> 54.35%
-97	PostVerifyDatabaseHandler.java	60.58% -> 3.52%

Cause

In .github/workflows/mvn-test.yml, coverage-report is wired to consume HA coverage but never waits for it:

coverage-report:
  needs: [ unit-tests, integration-tests, slow-unit-tests ]   # ha-integration-tests is absent
  ...
  - name: Download HA integration test coverage reports        # line ~757
    uses: actions/download-artifact@...
    continue-on-error: true                                    # failure is swallowed
    with:
      name: ha-integration-coverage-reports

ha-integration-tests does upload that artifact (line ~340, if: success() || failure()), so the intent is clearly
that HA coverage be included. But because the job is not in needs, coverage-report starts as soon as the three
listed jobs finish, while ha-integration-tests runs for ~55 minutes - by far the longest job in the workflow. The
artifact does not exist yet, continue-on-error: true hides that, and the merged report silently omits the whole
ha-raft module.

So the project total is computed against a base that included HA coverage and a head that does not. The gap is
roughly -0.76pp, which is enough to trip the threshold.

Why it matters

This is not specific to one PR - it is structural, and it fires on every PR whose other jobs finish before the HA
suite. The practical effect is that codecov/project is red for reasons unrelated to the diff, which trains
reviewers to ignore it. A coverage gate that is always red is worse than no gate: a real coverage regression would
look exactly like the noise.

Note codecov/patch is unaffected and remains meaningful (it scored the #5685 diff at 87.75% and passed), as do
Codacy Diff Coverage and Codacy Coverage Variation.

Suggested fix

Add the missing dependency:

coverage-report:
  needs: [ unit-tests, integration-tests, slow-unit-tests, ha-integration-tests ]

coverage-report already has if: success() || failure(), so adding the dependency does not make a failing HA suite
block the coverage report - it only makes it wait, which is what the existing download step assumes.

Two things worth deciding alongside:

1. continue-on-error: true on the download hides exactly this class of bug. Consider failing the job when an
   expected coverage artifact is missing, or at minimum logging which artifacts were skipped, so an incomplete
   upload is visible rather than silently reported as a coverage drop.
2. ha-integration-tests is currently failing on main most of the time (filed separately). While that is true,
   its coverage artifact still uploads (if: success() || failure()), so this fix works regardless - but the two
   interact, and fixing only this one will surface partial HA coverage from partially-failed runs.

Found while diagnosing a spurious codecov/project failure on #5685 (issue #5677).