What

Raise the coverage gate introduced in PR #619 from the current initial floor of 78% up to the full 80% line / 70% branch target from the original AC of #613.

Why

PR #619 merged an enforced coverage gate at 78% (current measured baseline: 78.3% line, branches unmeasured). The 80% target from #613 was reduced to 78% as an interim floor because pushing for the remaining 1.7% would have expanded the gate PR scope significantly. Raising the gate to 80% requires either repairing the pre-existing failing tests or adding new coverage.

How

Option A: repair pre-existing failing tests (higher ROI)

These tests are already failing on develop but not blocking CI because ctest runs with || true. Repairing them restores intended coverage:

• EncryptedWriterTest.WriteAndDecryptSingleEntry — format/magic mismatch (header.magic=842019419 vs kMagic=1162756946)
• EncryptedWriterTest.WriteMultipleEntries — same root cause
• LoggerOtelIntegrationTest.LoggerContextMethods
• ConsoleWriterIntegrityTest.RoundTripOnStdout

Option B: add new cases in the lowest-covered files

Per lcov per-file breakdown from the PR #619 CI run:

• logger.cpp — 63.6% (152 missed lines, largest absolute gap)
• encrypted_writer.cpp — 63.9% (104 missed)
• log_sampler.cpp — 60.1% (126 missed)

Option C: enable branch instrumentation

The gate currently skips branch coverage because lcov reports "no data found". Enabling branch instrumentation in the Debug+coverage build will produce a measurement and close the 70% branch AC from #613.

Acceptance criteria

• Coverage gate raised to LINE_THRESHOLD=80
• Either: failing tests above repaired OR equivalent new cases added
• Branch instrumentation enabled and BRANCH_THRESHOLD=70 enforced
• CI Coverage Analysis passes on a PR to develop

Context

• Parent issue: test: raise coverage from ~65% to 80% #613 (closed by PR ci(coverage): enforce 80% line / 70% branch coverage gate #619 with the gate + fixes)
• Merge commit: see PR ci(coverage): enforce 80% line / 70% branch coverage gate #619