feat: Add Python plugins from AutoMetabuilder + restructure workflow folder

Restructure workflow/ for multi-language plugin support:
- Rename src/ to core/ (engine code: DAG executor, registry, types)
- Create executor/{cpp,python,ts}/ for language-specific runtimes
- Consolidate plugins to plugins/{ts,python}/ by language then category

Add 80+ Python plugins from AutoMetabuilder in 14 categories:
- control: bot control, switch logic, state management
- convert: type conversions (json, boolean, dict, list, number, string)
- core: AI requests, context management, tool calls
- dict: dictionary operations (get, set, keys, values, merge)
- list: list operations (concat, find, sort, slice, filter)
- logic: boolean logic (and, or, xor, equals, comparisons)
- math: arithmetic operations (add, subtract, multiply, power, etc.)
- string: string manipulation (concat, split, replace, format)
- notifications: Slack, Discord integrations
- test: assertion helpers and test suite runner
- tools: file operations, git, docker, testing utilities
- utils: filtering, mapping, reducing, condition branching
- var: variable store operations (get, set, delete, exists)
- web: Flask server, environment variables, JSON handling

Add language executor runtimes:
- TypeScript: direct import execution (default, fast startup)
- Python: child process with JSON stdin/stdout communication
- C++: placeholder for native FFI bindings (Phase 3)

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

workflow/plugins/python/math/__init__.py

@@ -0,0 +1 @@
+"""Mathematical operations plugins."""

workflow/plugins/python/math/math_abs.py

@@ -0,0 +1,7 @@
+"""Workflow plugin: absolute value."""
+
+
+def run(_runtime, inputs):
+    """Calculate absolute value."""
+    value = inputs.get("value", 0)
+    return {"result": abs(value)}

workflow/plugins/python/math/math_add.py

@@ -0,0 +1,7 @@
+"""Workflow plugin: add numbers."""
+
+
+def run(_runtime, inputs):
+    """Add two or more numbers."""
+    numbers = inputs.get("numbers", [])
+    return {"result": sum(numbers)}

workflow/plugins/python/math/math_divide.py

@@ -0,0 +1,12 @@
+"""Workflow plugin: divide numbers."""
+
+
+def run(_runtime, inputs):
+    """Divide a by b."""
+    a = inputs.get("a", 0)
+    b = inputs.get("b", 1)
+
+    if b == 0:
+        return {"result": None, "error": "Division by zero"}
+
+    return {"result": a / b}

workflow/plugins/python/math/math_max.py

@@ -0,0 +1,11 @@
+"""Workflow plugin: maximum value."""
+
+
+def run(_runtime, inputs):
+    """Find maximum value in numbers."""
+    numbers = inputs.get("numbers", [])
+
+    if not numbers:
+        return {"result": None}
+
+    return {"result": max(numbers)}

workflow/plugins/python/math/math_min.py

@@ -0,0 +1,11 @@
+"""Workflow plugin: minimum value."""
+
+
+def run(_runtime, inputs):
+    """Find minimum value in numbers."""
+    numbers = inputs.get("numbers", [])
+
+    if not numbers:
+        return {"result": None}
+
+    return {"result": min(numbers)}

workflow/plugins/python/math/math_modulo.py

@@ -0,0 +1,12 @@
+"""Workflow plugin: modulo operation."""
+
+
+def run(_runtime, inputs):
+    """Calculate a modulo b."""
+    a = inputs.get("a", 0)
+    b = inputs.get("b", 1)
+
+    if b == 0:
+        return {"result": None, "error": "Modulo by zero"}
+
+    return {"result": a % b}

workflow/plugins/python/math/math_multiply.py

@@ -0,0 +1,10 @@
+"""Workflow plugin: multiply numbers."""
+
+
+def run(_runtime, inputs):
+    """Multiply two or more numbers."""
+    numbers = inputs.get("numbers", [])
+    result = 1
+    for num in numbers:
+        result *= num
+    return {"result": result}

workflow/plugins/python/math/math_power.py

@@ -0,0 +1,8 @@
+"""Workflow plugin: power operation."""
+
+
+def run(_runtime, inputs):
+    """Calculate a to the power of b."""
+    a = inputs.get("a", 0)
+    b = inputs.get("b", 1)
+    return {"result": a ** b}

workflow/plugins/python/math/math_round.py

@@ -0,0 +1,8 @@
+"""Workflow plugin: round number."""
+
+
+def run(_runtime, inputs):
+    """Round number to specified precision."""
+    value = inputs.get("value", 0)
+    precision = inputs.get("precision", 0)
+    return {"result": round(value, precision)}

workflow/plugins/python/math/math_subtract.py

@@ -0,0 +1,8 @@
+"""Workflow plugin: subtract numbers."""
+
+
+def run(_runtime, inputs):
+    """Subtract b from a."""
+    a = inputs.get("a", 0)
+    b = inputs.get("b", 0)
+    return {"result": a - b}