feat(comm): add inbox long polling

[ohdearquant]

AI-assisted contribution: Codex prepared this change and PR description.

Summary

• add optional, bounded wait_ms long-poll semantics to comm.inbox while preserving the existing filtering and pagination response shapes
• wake blocked inbox calls after successful local sends, replies, and non-deduplicated ingests using a generation-counted process-local signal that does not lose notifications between query and wait
• make the deadline edge race-safe with a final generation-aware query, cap waits at 30 seconds, and document process-local versus cross-process behavior
• add concurrent-ingest, filtering, timeout, cap, zero-wait, missed-wakeup, and deadline-crossing regressions

Closes #1499.

Test plan

• cargo test --manifest-path crates/Cargo.toml --workspace
• cargo check --manifest-path crates/Cargo.toml --workspace
• cargo clippy --manifest-path crates/Cargo.toml --workspace --all-targets -- -D warnings
• cargo fmt --manifest-path crates/Cargo.toml --all -- --check
• RUSTDOCFLAGS=-Dwarnings cargo doc --manifest-path crates/Cargo.toml --workspace --no-deps

All commands passed at 0a0c7e515b051f243eb1d3a73928c35bb2857527 after rebasing onto current main (a152ead3e577b8c01b03024687fdb66d94a00cac).

ADR

• update ADR-040 with the public wait_ms contract and response-shape guarantees
• update ADR-056 with signal ownership, generation semantics, publication points, deadline behavior, and the cross-process boundary

AI-assisted contribution checklist

• Every claim in this PR description matches the actual diff
• Any agent-authored comment / PR body starts with an attribution line
• Full workspace behavior, lint, formatting, and documentation gates passed
• No entity, note, edge, namespace, delivery, or threading semantics changed

Out of scope

• cross-process push notification; external writers are observed by the final deadline query rather than waking the process-local signal immediately
• changing channel transport poll intervals
• changing inbox pagination or filter semantics