feat: add data-platform plugin (v4.0.0)

Add new data-platform plugin for data engineering workflows with:

MCP Server (32 tools):
- pandas operations (14 tools): read_csv, read_parquet, read_json,
  to_csv, to_parquet, describe, head, tail, filter, select, groupby,
  join, list_data, drop_data
- PostgreSQL/PostGIS (10 tools): pg_connect, pg_query, pg_execute,
  pg_tables, pg_columns, pg_schemas, st_tables, st_geometry_type,
  st_srid, st_extent
- dbt integration (8 tools): dbt_parse, dbt_run, dbt_test, dbt_build,
  dbt_compile, dbt_ls, dbt_docs_generate, dbt_lineage

Plugin Features:
- Arrow IPC data_ref system for DataFrame persistence across tool calls
- Pre-execution validation for dbt with `dbt parse`
- SessionStart hook for PostgreSQL connectivity check (non-blocking)
- Hybrid configuration (system ~/.config/claude/postgres.env + project .env)
- Memory management with 100k row limit and chunking support

Commands: /initial-setup, /ingest, /profile, /schema, /explain, /lineage, /run
Agents: data-ingestion, data-analysis

Test suite: 71 tests covering config, data store, pandas, postgres, dbt tools

Addresses data workflow issues from personal-portfolio project:
- Lost data after multiple interactions (solved by Arrow IPC data_ref)
- dbt 1.9+ syntax deprecation (solved by pre-execution validation)
- Ungraceful PostgreSQL error handling (solved by SessionStart hook)

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

scripts/setup.sh

@@ -116,6 +116,15 @@ verify_symlinks() {
         log_error "pr-review/gitea symlink missing"
         log_todo "Run: ln -s ../../../mcp-servers/gitea plugins/pr-review/mcp-servers/gitea"
     fi
+
+    # Check data-platform -> data-platform symlink
+    local dataplatform_link="$REPO_ROOT/plugins/data-platform/mcp-servers/data-platform"
+    if [[ -L "$dataplatform_link" ]]; then
+        log_success "data-platform symlink exists"
+    else
+        log_error "data-platform symlink missing"
+        log_todo "Run: ln -s ../../../mcp-servers/data-platform plugins/data-platform/mcp-servers/data-platform"
+    fi
 }
 
 # --- Section 3: Config File Templates ---
@@ -178,6 +187,22 @@ EOF
         chmod 600 "$config_dir/git-flow.env"
         log_success "git-flow.env template created"
     fi
+
+    # PostgreSQL config (for data-platform, optional)
+    if [[ -f "$config_dir/postgres.env" ]]; then
+        log_skip "postgres.env already exists"
+    else
+        cat > "$config_dir/postgres.env" << 'EOF'
+# PostgreSQL Configuration (for data-platform plugin)
+# Update with your PostgreSQL connection URL
+# This is OPTIONAL - pandas tools work without it
+
+POSTGRES_URL=postgresql://user:password@localhost:5432/database
+EOF
+        chmod 600 "$config_dir/postgres.env"
+        log_success "postgres.env template created"
+        log_todo "Edit ~/.config/claude/postgres.env with your PostgreSQL credentials (optional)"
+    fi
 }
 
 # --- Section 4: Validate Configuration ---
@@ -283,6 +308,7 @@ main() {
     # Shared MCP servers at repository root
     setup_shared_mcp "gitea"
     setup_shared_mcp "netbox"
+    setup_shared_mcp "data-platform"
 
     # Verify symlinks from plugins to shared MCP servers
     verify_symlinks