fix(acp): re-root custom log targets under buzz_acp

[troyhoffman-oss]

The default filter is buzz_acp=info — set in run() and matched by the desktop's child-process filter in managed_agents/runtime.rs — but 84 log sites across the message-handling path declare their own target: pool::session, pool::prompt, acp::wire, canvas::fetch, and a dozen more.

EnvFilter matches a target by prefix from its root, and none of those roots is buzz_acp, so every one of them is filtered out. Turn dispatch, wire traffic, and session lifecycle never appear in a production journal, and RUST_LOG=buzz_acp=debug — the line TESTING.md hands operators when the default log is too quiet — turns none of them on.

This is the mechanism behind an observation in #2795: that fix's only trace was "a pool::model WARN that never reaches the per-agent log files."

Each target is now prefixed with buzz_acp::, so the crate filter reaches them while the existing suffixes keep working as narrower selectors (RUST_LOG=buzz_acp::acp::wire=trace). Names are otherwise unchanged, and nothing outside these call sites referenced them.

Pure rename — 84 insertions, 84 deletions, every changed line a target: string. No behavior change beyond the logs becoming reachable.

Testing

cargo test -p buzz-acp --lib: 616 passed; 0 failed. cargo fmt --check and cargo clippy -p buzz-acp --all-targets clean.