feat: plane-2 rules read declared param roles instead of guessing args

Add ParamRole and a defaulted Tool.paramRoles to the tool contract; built-in
tools declare which params carry effects: file_read/write/edit -> path=PATH,
shell -> argv=EXEC_COMMAND. PathContainmentRule / ExecInterpreterRule /
NetworkHostRule now inspect only the declared params when roles are present, and
fall back to the looksLikePath / leading-token / extractHost heuristic only for
un-enriched (e.g. custom) tools - so a custom FILE_WRITE tool is still
containment-checked. Shared extractParamStrings flattens String and List<*>
(argv) values. SessionOrchestrator.runPlane2Assessment resolves the tool once
and passes tool.paramRoles into the assessment input.

This retires the arg-guessing from the first-party path: a slashy edit 'content'
arg is no longer mis-flagged as a path.

core/tools/src/main/kotlin/com/correx/core/tools/contract/ParamRole.kt

@@ -0,0 +1,3 @@
+package com.correx.core.tools.contract
+
+enum class ParamRole { PATH, EXEC_COMMAND, NETWORK_TARGET }

core/tools/src/main/kotlin/com/correx/core/tools/contract/Tool.kt

@@ -10,5 +10,6 @@ interface Tool {
     val parametersSchema: JsonObject
     val tier: Tier
     val requiredCapabilities: Set<ToolCapability>
+    val paramRoles: Map<String, ParamRole> get() = emptyMap()
     fun validateRequest(request: ToolRequest): ValidationResult
 }