update the codebase poc ver1

AGENT_SKILL/agent_tool_execution/SKILL.md

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+# Skill: agent_tool_execution
+
+## Trigger Conditions
+
+Any change involving Gemma-4-E2B agent tools, Exa search, Supabase RAG RPC, or MedGemma escalation.
+
+## Rules
+
+### 1. Tool catalog is authoritative
+
+- Only use: `exa_search`, `supabase_query`, `escalate_medgemma`.
+- Never invent tool names in prompts or handlers.
+- Bump `TOOL_CATALOG_VERSION` on breaking schema changes.
+
+### 2. Secrets and egress
+
+- `EXA_API_KEY`, `SUPABASE_SERVICE_ROLE_KEY`, MedGemma keys: **backend only**.
+- Browser calls BFF routes; never `https://api.exa.ai` directly from the client.
+- PHI-scrub queries before any network egress ([`secrets_and_phi_safety`](../secrets_and_phi_safety/SKILL.md)).
+
+### 3. Exa defaults (Pattern 1 — raw retrieval)
+
+```json
+{
+  "type": "auto",
+  "numResults": 10,
+  "contents": { "highlights": true }
+}
+```
+
+- Canonical reference: https://docs.exa.ai/reference/search-api-guide-for-coding-agents
+- Do not use deprecated params (`useAutoprompt`, top-level `highlights`, `livecrawl: "always"`).
+- `outputSchema` synthesis is BFF-only enrichment; not the default agent-loop path.
+
+### 4. Retrieval policy (NFR-18)
+
+- `supabase_query` first for in-corpus MOH guideline grounding.
+- `exa_search` for external/recency queries.
+- Final clinical answers must cite chunk IDs (Supabase) or URLs (Exa).
+
+### 5. MedGemma escalation
+
+- Requires consent + audit (NFR-16a) before `escalate_medgemma`.
+- No direct Modal URLs from the browser.
+
+### 6. MediaPipe agent output
+
+- Parse tool calls from the **answer channel** when CoT is enabled.
+- One block per turn: `<tool_call>` OR `<final>`.
+
+## Package location
+
+[`ml/implementation/nlp/agent_runtime/`](../ml/implementation/nlp/agent_runtime/)