fix: complete all P3 audit findings — empty modules, docs drift, detekt, worktree

P3-1: Delete 17 empty Gradle modules (core:agents/observability/policies/stages,
      infrastructure:scheduler/security/telemetry, all 7 plugins/*, all 3
      interfaces/*). Zero source files, zero dependents, identical build.gradle
      stubs. Remove from settings.gradle. Keep .adoc spec docs as roadmap refs.
P3-2: Fix docs drift — rename :core:orchestration to :core:kernel in
      core-orchestration-submodule-spec.md, rewrite stale chat-transcript
      modules-and-spec.md as proper doc.
      (CLAUDE.md Router context isolation clarification is local-only,
       file is gitignored.)
P3-3: Reduce detekt maxIssues from 999999 to 120 (actual current count ~107).
      (CLAUDE.md detekt description updated locally; file is gitignored.)
P3-4: Remove stale locked worktree agent-a98d45277ce4b0040 (contained only
      cosmetic test style changes and an unused kotlinx-datetime dep).

core/agents/build.gradle

@@ -1,5 +0,0 @@
-plugins {
-    id 'java-library'
-    id 'org.jetbrains.kotlin.jvm'
-    id 'org.jetbrains.kotlin.plugin.serialization'
-}

core/observability/build.gradle

@@ -1,5 +0,0 @@
-plugins {
-    id 'java-library'
-    id 'org.jetbrains.kotlin.jvm'
-    id 'org.jetbrains.kotlin.plugin.serialization'
-}

core/policies/build.gradle

@@ -1,5 +0,0 @@
-plugins {
-    id 'java-library'
-    id 'org.jetbrains.kotlin.jvm'
-    id 'org.jetbrains.kotlin.plugin.serialization'
-}

core/stages/build.gradle

@@ -1,5 +0,0 @@
-plugins {
-    id 'java-library'
-    id 'org.jetbrains.kotlin.jvm'
-    id 'org.jetbrains.kotlin.plugin.serialization'
-}