Merge origin/main into duncan/byoh-generic-acp-harness

Main's #2974 modularized managed_agents/runtime.rs (process / orphan_sweep /
instance_reaper / lifecycle / metadata) from pre-PR content, conflicting with
this PR's runtime.rs changes. Resolution re-applies the PR's semantics into
the new module layout, changing nothing else:

- process.rs: valid_agent_runtime_receipt delegates to injectable
  valid_agent_runtime_receipt_with; marker-only ownership (name gate dropped).
- orphan_sweep.rs: sweep ownership rule comment block; marker-only gates in
  sweep_orphaned/sweep_system/collect_same_instance_orphans (macOS + Linux).
- instance_reaper.rs: name pre-gate removed on both platforms (marker is the
  authoritative proof).
- lifecycle.rs: kill_stale_tracked_processes delegates to injectable
  kill_stale_tracked_processes_with.
- runtime.rs: build_managed_agent_summary/spawn_agent_child keep the PR's
  descriptor resolver, global_config param, MissingBinary requirement, and
  descriptor.env write-back (main refactor did not touch these hunks);
  cfg(test) re-exports added for the injectable seams.
- check-file-sizes.mjs: took main's side (runtime.rs override removed by
  #2974; post-merge runtime.rs is 944 lines, under the 1000 ceiling).
  runtime/tests.rs keeps the PR's 1320 ratchet.

Verified at merge tree: cargo test --lib 1705/0 (14 ignored), clippy -D
warnings, fmt, file-size gate all clean.

Co-authored-by: Tyler Longwell <tlongwell@block.xyz>
Signed-off-by: Tyler Longwell <tlongwell@block.xyz>

desktop/scripts/check-file-sizes.mjs

@@ -122,32 +122,6 @@ const overrides = new Map([
   // helpers) replace the pubkey-keyed PID file, plus the hashed pair-scoped
   // runtime log path. Load-bearing crash-recovery surface; queued to split.
   ["src-tauri/src/managed_agents/storage.rs", 1383],
-  // harness-persona-sync: persona-runtime resolution threaded into the spawn
-  // path here. Load-bearing feature growth; queued to split in the resolver
-  // unify refactor followup. +26 for resolve_effective_prompt_model_provider
-  // re-introduced after 826d735fe removal (config-bridge caller still needs it).
-  // PGID resolution helper + PID-recycling safety guard added for orphan sweep.
-  // activity-feed threads avatar_url into build_managed_agent_summary for the
-  // assistant-bubble pinned snapshot.
-  // +1 for agent_pubkey field in setup payload (config-nudge card wire).
-  // persona-blank-fallback: resolve_effective_prompt_model_provider gains a
-  // record_provider param + applies persona_field_with_record_fallback. +5 lines.
-  // global-agent-config: spawn_agent_child loads global config and merges as
-  // lowest env layer (+8 lines). Queued to split.
-  // +2: BYOH orphan-sweep fix — `!belongs && !has_buzz_marker` OR-gate replaces
-  // the old AND-gate so custom harness processes are not silently leaked on crash.
-  // +27: BYOH F4 fix — extract shared `buzz_sweep_owns_process` predicate, fix
-  // Linux AND-gate in sweep + orphan collectors, 4 production predicate tests.
-  // +12: BYOH F2 — record_agent_command / effective_agent_command check loaded
-  // harness registry for preset/custom ids after static-builtin lookup.
-  // +61: BYOH pass-2 — I2 (spawn_agent_child env+args from definition), I3
-  // (valid_agent_runtime_receipt uses buzz_sweep_owns_process marker-only),
-  // I6 (cross-platform buzz_sweep_owns_process, drop #[cfg(unix)]), +2 new
-  // receipt-path collector-decision tests.
-  // +2: BYOH Phase A — resolve_effective_harness_descriptor single typed resolver;
-  // C-9 injectable sweep predicates (kill_stale_tracked_processes_with +
-  // valid_agent_runtime_receipt_with) with 5 discriminating tests.
-  ["src-tauri/src/managed_agents/runtime.rs", 2326],
   // config-bridge setup-payload env-boundary fix adds readiness wiring in
   // spawn_agent_child; load-bearing security fix, queued to split.
   ["src-tauri/src/managed_agents/config_bridge/reader.rs", 1016],