fix(subprocess): tree-scoped escalation and byte-exact tails (Codex round 1)

(A1) terminate()/dispose()/service teardown keyed on direct-child settlement
could leak a TERM-trapping descendant that outlived the leader (Codex
reproduced it with a disowned trap-SIGTERM helper). kill()/terminate() now
gate on tree liveness instead of outcome settlement; the SIGKILL escalation
timer survives settle (unref'd, re-probing the tree); dispose's tier
quiescence is whole-tree exit via a bounded waitForExit; the service's live
set releases handles only when their tree is gone, and its teardown awaits
tree exit. Three new suites pin the survivor scenarios end to end
(terminate, dispose, service teardown).

(A2) the escalation branch is now real tested behavior — its ignore is gone;
the one remaining signalTree guard ignore states why it is unreachable
through the handle verbs.

(A3) docs contradictions fixed: the impl README's stale POSIX-only bullet
now states the contained best-effort Windows tree story; the lsp-local
README no longer claims taskkill failures stay visible (containment + the
tree-liveness wait is the actual contract); the architecture tables (en+zh)
list all three consumer families.

(B1) OutputCollector keeps a byte-exact tail across uneven chunk boundaries
(trim the head chunk instead of dropping it whole) — the LSP diagnostic-tail
contract; pinned by a cross-chunk test.

(B2) the subagent-acp coverage ignore is narrowed to exactly the
never-settling success arm.

docs/architecture.i18n.yaml

@@ -2,5 +2,5 @@
 # side as of the last confirmed-consistent state. Both languages carry equal authority;
 # after editing either side, bring the other along and re-record with:
 #   pnpm run verify-translation-pairing --write
-architecture.md: 9c4c9fc12a51c9c49d02a7aa9c3633ae7c95e4fe
-architecture.zh.md: bc6adef969f60e7a7522a1877d29b2f90fc0c322
+architecture.md: 8334153482843f26defa8d175042a1349d6c9eca
+architecture.zh.md: bb874654496bc9d131b1d7529c3585ed4682c0cf