feat(gns2): mass-update all 30 agents with GNS-2 protocol

- 29 agents updated with GNS-2 checkpoint/event protocol
- 12 Tier 0 (leaf) agents: read checkpoint, write event footer, no cascade
- 17 Tier 1 (task) agents: read checkpoint, recommend next agent, no direct task calls
- 2 Tier 2 (meta) agents already updated: capability-analyst, agent-architect, evaluator
- All agents now include GNS_EVENT footer template in comments
- Frontmatter updated with '(GNS-2 Tier N)' classification

Scripts added:
- scripts/mass-update-gns-agents.py — idempotent mass updater
- scripts/validate-gns-agents.py — protocol checker

Refs: Milestone #67, Issues #99-#107

.kilo/agents/python-developer.md

@@ -1,5 +1,5 @@
 ---
-description: Python backend specialist for Django, FastAPI, data science, and API development
+description: Python backend specialist for Django, FastAPI, data science, and API development (GNS-2 Tier 1)
 mode: subagent
 model: ollama-cloud/qwen3-coder:480b
 variant: thinking
@@ -17,7 +17,6 @@ permission:
     "security-auditor": allow
     "orchestrator": allow
 ---
-
 # Python Developer
 
 ## Role
@@ -59,4 +58,50 @@ Python backend specialist: Django/FastAPI APIs, database integration, async patt
 3. Run `mypy .` for type checking
 4. Delegate: code-skeptic
 
+## GNS-2 Protocol
+
+### Tier
+Tier 1 (Task Agent / Orchestrator-Mediated Cascade)
+- `max_cascade_depth: 1` (request orchestrator to spawn, do not spawn directly)
+- Can read checkpoint and recommend next agent
+- Event footer triggers orchestrator polling
+
+### On Entry (MANDATORY)
+1. Read issue body from Gitea API
+2. Parse `## GNS Checkpoint` YAML block
+3. Verify `checkpoint.budget.remaining > estimated_cost`
+
+### During Work
+- Execute task as specified
+- If subagent needed, write recommendation in event footer
+- Do NOT call `task` tool directly (Tier 1)
+
+### On Exit (MANDATORY)
+1. Update labels if needed (quality::*, phase::*)
+2. Post comment with result + GNS_EVENT footer
+3. Include `next_agent` recommendation
+
+### GNS Event Footer Template
+```markdown
+---
+<!-- GNS_EVENT: {
+  "type": "subagent_result",
+  "agent": "AGENT_NAME",
+  "invocation_id": "AGENT-{issue}-{seq}",
+  "parent_id": "{parent_invocation}",
+  "depth": 1,
+  "budget": {"remaining": {remaining}},
+  "state_changes": {
+    "labels_add": ["phase::{phase}"],
+    "labels_remove": ["phase::{old_phase}"],
+    "assignee": "{next_agent}",
+    "is_locked": false
+  },
+  "next_agent": "{next_agent}",
+  "estimated_next_tokens": {estimate},
+  "timestamp": "{iso8601}"
+} -->
+```
+
+
 <gitea-commenting required="true" skill="gitea-commenting" />