test(shared): cover the LLDB policy wrappers' own members - cpp 36%->100%, rust 71%->100%

[debugmcpdev]

Why

adapter-policy-cpp.ts sat at 35.7% lines / 0% branches on the coverage leaderboard while every other policy read 70-100%. Investigation showed the number is mostly a measurement artifact of the file's structure, not missing behavioral tests:

• The cpp policy is a thin composition wrapper: 15 of its members are bare references into lldb-policy-shared.ts (94% lines, 100% functions). Its 234-line unit test exercises stop-reason normalization, stack filtering, variable extraction, state tracking, and spawn config heavily - but istanbul credits all of that to the shared file.
• Only 14 statements / 11 inline functions belong to the wrapper itself, so the 7 trivial one-liners no test happened to call dragged it to 35%, and always-explicit platform/arch args left the default-arg branches at 0/4.
• Rust is structurally identical and sat at 70.6% - second-lowest - for the same reason. No compiler, CodeLLDB binary, or platform skip-gate involved.

Changes (test-only, no source changes)

• adapter-policy-cpp.test.ts: call the 7 uncalled members (buildChildStartArgs throw, isChildReadyEvent, getLocalScopeName, resolveExecutablePath both arms, getDebuggerConfiguration, requiresCommandQueueing, shouldQueueCommand) plus one getAdapterSpawnConfig call omitting platform/arch so the default-arg branches fire.
• adapter-policy-rust.test.ts: same treatment for rust's 5 missed members (isChildReadyEvent, getLocalScopeName, getDapAdapterConfiguration, getDebuggerConfiguration, requiresCommandQueueing).
• resolve-exception-filters.test.ts: add cpp to the guardrail matrix (uncaught: [], all: ['cpp_throw'], default 'uncaught'). Cpp was the only policy with an exception-filter table missing from the test whose stated purpose is that filter-table changes must be deliberate - a real consistency gap surfaced by the investigation.

Coverage result (verified locally, istanbul)

File	Before (lines/branches/funcs)	After
adapter-policy-cpp.ts	35.7% / 0% / 36.4%	100% / 100% / 100%
adapter-policy-rust.ts	70.6% / 100% / 58.3%	100% / 100% / 100%

Full unit suite: 214 files / 3844 tests passing; pre-push lint + build + unit + integration all green.

🤖 Generated with Claude Code

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.

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