feat(task-system): add experimental task system with Claude Code spec alignment (#1415)

* feat(hooks): add tasks-todowrite-disabler hook to block TodoRead/TodoWrite

Ultraworked with [Sisyphus](https://github.com/code-yeongyu/oh-my-opencode)

Co-authored-by: Sisyphus <clio-agent@sisyphuslabs.ai>

* feat(task-tools): add parallel execution guidance to descriptions

Ultraworked with [Sisyphus](https://github.com/code-yeongyu/oh-my-opencode)

Co-authored-by: Sisyphus <clio-agent@sisyphuslabs.ai>

* refactor(index): migrate task system to experimental.task_system flag

Ultraworked with [Sisyphus](https://github.com/code-yeongyu/oh-my-opencode)

Co-authored-by: Sisyphus <clio-agent@sisyphuslabs.ai>

* docs: update AGENTS.md for experimental task system

Ultraworked with [Sisyphus](https://github.com/code-yeongyu/oh-my-opencode)

Co-authored-by: Sisyphus <clio-agent@sisyphuslabs.ai>

* fix(task-tests): align test field names with Claude Code spec (subject, blockedBy, addBlockedBy)

* fix: address Cubic review feedback

Ultraworked with [Sisyphus](https://github.com/code-yeongyu/oh-my-opencode)

Co-authored-by: Sisyphus <clio-agent@sisyphuslabs.ai>

* fix: add optional chaining for tasksTodowriteDisabler null check

---------

Co-authored-by: Sisyphus <clio-agent@sisyphuslabs.ai>

src/hooks/tasks-todowrite-disabler/constants.ts

@@ -0,0 +1,10 @@
+export const HOOK_NAME = "tasks-todowrite-disabler"
+export const BLOCKED_TOOLS = ["TodoWrite", "TodoRead"]
+export const REPLACEMENT_MESSAGE = `TodoRead/TodoWrite are disabled because experimental.task_system is enabled.
+Use the new task tools instead:
+- TaskCreate: Create new tasks with auto-generated IDs
+- TaskUpdate: Update task status, add dependencies
+- TaskList: List active tasks with dependency info
+- TaskGet: Get full task details
+
+IMPORTANT: 1 task = 1 delegate_task. Maximize parallel execution by running independent tasks concurrently.`