fix: replace remaining bioRxiv refs with Europe PMC in docs

Files updated:
- 09_phase_source_cleanup.md: Literal type in preview code
- 10_phase_clinicaltrials.md: Literal type in preview code
- 13_phase_modal_integration.md: MCP tools diagram
- 14_phase_demo_submission.md: Demo script, HF README template, social media

These are documentation files showing what the tool does.
The actual implementation uses Europe PMC (not bioRxiv).

docs/implementation/09_phase_source_cleanup.md

@@ -62,7 +62,7 @@ sources_searched: list[Literal["pubmed", "web"]]
 sources_searched: list[Literal["pubmed"]]
 
 # AFTER (Phase 10-11)
-sources_searched: list[Literal["pubmed", "clinicaltrials", "biorxiv"]]
+sources_searched: list[Literal["pubmed", "clinicaltrials", "europepmc"]]
 ```
 
 ### 2.4 DELETE: Tests for WebTool

docs/implementation/10_phase_clinicaltrials.md

@@ -90,7 +90,7 @@ InterventionName, StartDate, CompletionDate, BriefSummary
 source: Literal["pubmed", "web"]
 
 # AFTER
-source: Literal["pubmed", "clinicaltrials", "biorxiv"]
+source: Literal["pubmed", "clinicaltrials", "europepmc"]
 ```
 
 ### 3.2 Evidence from Clinical Trials

docs/implementation/13_phase_modal_integration.md

@@ -1133,7 +1133,7 @@ Phase 13 is **COMPLETE** when:
 ┌─────────────────────────────────────────────────────────────────┐
 │                     Gradio App + MCP Server                     │
 │  ┌──────────────────────────────────────────────────────────┐   │
-│  │  MCP Tools: search_pubmed, search_trials, search_biorxiv │   │
+│  │  MCP Tools: search_pubmed, search_trials, search_europepmc │   │
 │  │             search_all, analyze_hypothesis               │   │
 │  └──────────────────────────────────────────────────────────┘   │
 └───────────────────────────┬─────────────────────────────────────┘

docs/implementation/14_phase_demo_submission.md

@@ -86,7 +86,7 @@ to find new uses for existing drugs."
 "When I ask about metformin for Alzheimer's, DeepBoner:
 1. Searches PubMed for peer-reviewed papers
 2. Queries ClinicalTrials.gov for active trials
-3. Scans bioRxiv for the latest preprints"
+3. Scans Europe PMC for the latest preprints"
 
 [Show search results streaming]
 
@@ -189,7 +189,7 @@ AI-Powered Drug Repurposing Research Agent
 
 ## Features
 
-- **Multi-Source Search**: PubMed, ClinicalTrials.gov, bioRxiv/medRxiv
+- **Multi-Source Search**: PubMed, ClinicalTrials.gov, Europe PMC (incl. preprints)
 - **MCP Integration**: Use our tools from Claude Desktop or any MCP client
 - **Modal Sandbox**: Secure execution of AI-generated statistical code
 - **LlamaIndex RAG**: Semantic search and evidence synthesis
@@ -204,7 +204,7 @@ https://your-space.hf.space/gradio_api/mcp/
 Available tools:
 - `search_pubmed` - Search peer-reviewed biomedical literature
 - `search_clinical_trials` - Search ClinicalTrials.gov
-- `search_biorxiv` - Search bioRxiv/medRxiv preprints
+- `search_europepmc` - Search Europe PMC (preprints & papers)
 - `search_all` - Search all sources simultaneously
 
 ## Team
@@ -240,7 +240,7 @@ MODAL_TOKEN_SECRET=...
 🧬 Excited to submit DeepBoner to MCP's 1st Birthday Hackathon!
 
 An AI agent that:
-✅ Searches PubMed, ClinicalTrials.gov & bioRxiv
+✅ Searches PubMed, ClinicalTrials.gov & Europe PMC
 ✅ Exposes tools via MCP protocol
 ✅ Runs statistical code in Modal sandboxes
 ✅ Uses LlamaIndex for semantic search