feat(controller): clusterconfig-schema-split task 1.1 — remove dead fields from ClusterConfig schema

Removes port, candidates, vcpus, jobmgr, workermgr, qmgr, resmgr, xstrings
from the ClusterConfig capnp struct plus the now-unused MasterCandidate
struct, per the config-design.md shared-vs-local classification rule.

Cap'n Proto forbids ordinal gaps, so the 13 retained fields are renumbered
to a contiguous @0..@12 (accepted pre-1.0 wire-compat break — see
research.md's "Design Revision 2"). requirements.md/design.md updated to
match: Req 3.1 drops field-number invariance, Req 3.2/4.1 state a pre-spec
cluster.bin is not expected to decode correctly, and a new Req 5.3 covers
regenerating the checked-in ha/data/cluster.bin fixture in a later task.

Also folds in this session's live design revision: Requirement 1.7's port
replacement mechanism is the existing --peers self-reference + a hardcoded
default (no new --port CLI flag), confirmed via interactive review with
the spec owner.

.kiro/specs/clusterconfig-schema-split/spec.json

@@ -0,0 +1,22 @@
+{
+  "feature_name": "clusterconfig-schema-split",
+  "created_at": "2026-07-20T00:29:00Z",
+  "updated_at": "2026-07-20T06:15:00Z",
+  "language": "en",
+  "phase": "tasks-generated",
+  "approvals": {
+    "requirements": {
+      "generated": true,
+      "approved": true
+    },
+    "design": {
+      "generated": true,
+      "approved": true
+    },
+    "tasks": {
+      "generated": true,
+      "approved": true
+    }
+  },
+  "ready_for_implementation": true
+}