Require explicit CrewAI project definitions (#6358)

* Require explicit CrewAI project definitions

JSON crews and declarative flows now resolve from `[tool.crewai]`
metadata instead of implicit filename discovery. This makes project type
selection deterministic, prevents stray `crew.json(c)` files from changing
CLI behavior, and centralizes definition path validation for run, install,
deploy validation, plotting, and memory reset paths.

`[tool.crewai].definition` must be a project-local file path. Absolute
paths, `~`, missing files, directories, and paths escaping the project root
are rejected so deploy and runtime commands use the same contract.

Breaking changes and migration paths:

* JSON crew projects are no longer discovered from `crew.json` or
  `crew.jsonc` alone. Add explicit metadata:

  ```toml
  [tool.crewai]
  type = "crew"
  definition = "crew.jsonc"
  ```

* Declarative flow projects must use a valid project-local definition path:

  ```toml
  [tool.crewai]
  type = "flow"
  definition = "flows/research.yaml"
  ```

* `Flow.from_definition(definition)` is removed. Use:

  ```python
  Flow.from_declaration(contents=definition)
  ```

* `FlowDefinition.to_json()` and `FlowDefinition.to_yaml()` are removed.
  Use `FlowDefinition.to_dict()` and serialize with the caller's JSON or
  YAML library.

* `FlowDefinition.from_dict()` is removed. Use:

  ```python
  FlowDefinition.from_declaration(contents=data)
  ```

* `FlowDefinition.json_schema()` is removed. Use Pydantic's schema API only
  where schema generation is intentionally needed:

  ```python
  FlowDefinition.model_json_schema(by_alias=True)
  ```

* `crewai_cli.run_crew.find_crew_json_file()` and `_has_json_crew()` are
  removed. Use `configured_project_json_crew()` or the shared
  `crewai_core.project.configured_project_definition("crew")` helper.

* `crewai reset-memories` now only loads JSON crews declared through
  `[tool.crewai].definition`, and invalid declared JSON crew definitions
  fail instead of silently falling back to classic crew discovery.

* Address code review comments

lib/cli/src/crewai_cli/deploy/validate.py

@@ -40,14 +40,18 @@ from typing import Any
 
 from crewai.project.json_loader import (
     JSONProjectValidationError,
-    find_crew_json_file,
     find_json_project_file,
     validate_crew_project,
 )
+from crewai_core.project import (
+    ProjectDefinitionError,
+    configured_project_definition,
+    get_crewai_project_config,
+    get_crewai_project_type,
+    read_toml,
+)
 from rich.console import Console
 
-from crewai_cli.utils import parse_toml
-
 
 console = Console()
 logger = logging.getLogger(__name__)
@@ -159,24 +163,16 @@ class DeployValidator:
 
     @property
     def _is_json_crew(self) -> bool:
-        """True for JSON crew projects, deferring to the declared type.
-
-        A flow project that also contains a crew.json(c) file validates as
-        the flow it declares in pyproject.toml, not as a JSON crew.
-        """
-        if find_crew_json_file(self.project_root) is None:
-            return False
+        """True for JSON crew projects with configured crew definitions."""
         pyproject_path = self.project_root / "pyproject.toml"
         if not pyproject_path.exists():
-            return True
+            return False
         try:
-            data = parse_toml(pyproject_path.read_text())
+            data = read_toml(pyproject_path)
         except Exception:
-            return True
-        declared_type: str | None = (
-            (data.get("tool") or {}).get("crewai", {}).get("type")
-        )
-        return declared_type != "flow"
+            return False
+        crewai_config = get_crewai_project_config(data)
+        return crewai_config.get("type") == "crew" and "definition" in crewai_config
 
     def run(self) -> list[ValidationResult]:
         """Run all checks. Later checks are skipped when earlier ones make
@@ -208,14 +204,32 @@ class DeployValidator:
 
     def _run_json_checks(self) -> list[ValidationResult]:
         """Validation suite for JSON-defined crew projects."""
-        crew_path = find_crew_json_file(self.project_root)
+        self._check_pyproject()
+        self._check_lockfile()
+
+        try:
+            crew_path = configured_project_definition(
+                "crew",
+                pyproject_data=self._pyproject,
+                project_root=self.project_root,
+            )
+        except ProjectDefinitionError as exc:
+            self._add(
+                Severity.ERROR,
+                "invalid_crew_definition",
+                "[tool.crewai] definition is invalid",
+                detail=str(exc),
+                hint=(
+                    "Set `[tool.crewai] definition` to a project-local JSON "
+                    "or JSONC crew file."
+                ),
+            )
+            return self.results
+
         if crew_path is None:
             return self.results
 
-        agents_dir = self.project_root / "agents"
-
-        self._check_pyproject()
-        self._check_lockfile()
+        agents_dir = crew_path.parent / "agents"
         agents_dir_ok = self._check_json_agents_dir(agents_dir)
 
         project = None
@@ -346,7 +360,7 @@ class DeployValidator:
             return False
 
         try:
-            self._pyproject = parse_toml(pyproject_path.read_text())
+            self._pyproject = read_toml(pyproject_path)
         except Exception as e:
             self._add(
                 Severity.ERROR,
@@ -374,9 +388,7 @@ class DeployValidator:
 
         self._project_name = name
         self._package_name = normalize_package_name(name)
-        self._is_flow = (self._pyproject.get("tool") or {}).get("crewai", {}).get(
-            "type"
-        ) == "flow"
+        self._is_flow = get_crewai_project_type(self._pyproject) == "flow"
         return True
 
     def _check_lockfile(self) -> None: