Refactor task management structure and update documentation

- Changed the directory structure for task specifications to include a dedicated `todo/` folder within `_docs/02_tasks/` for tasks ready for implementation.
- Updated references in various skills and documentation to reflect the new task lifecycle, including changes in the `implementer` and `decompose` skills.
- Enhanced the README and flow documentation to clarify the new task organization and its implications for the implementation process.

These updates improve task management clarity and streamline the implementation workflow.

.cursor/skills/implement/SKILL.md

@@ -33,12 +33,22 @@ The `implementer` agent is the specialist that writes all the code — it receiv
 ## Context Resolution
 
 - TASKS_DIR: `_docs/02_tasks/`
-- Task files: all `*.md` files in TASKS_DIR (excluding files starting with `_`)
+- Task files: all `*.md` files in `TASKS_DIR/todo/` (excluding files starting with `_`)
 - Dependency table: `TASKS_DIR/_dependencies_table.md`
 
+### Task Lifecycle Folders
+
+```
+TASKS_DIR/
+├── _dependencies_table.md
+├── todo/        ← tasks ready for implementation (this skill reads from here)
+├── backlog/     ← parked tasks (not scheduled yet, ignored by this skill)
+└── done/        ← completed tasks (moved here after implementation)
+```
+
 ## Prerequisite Checks (BLOCKING)
 
-1. TASKS_DIR exists and contains at least one task file — **STOP if missing**
+1. `TASKS_DIR/todo/` exists and contains at least one task file — **STOP if missing**
 2. `_dependencies_table.md` exists — **STOP if missing**
 3. At least one task is not yet completed — **STOP if all done**
 
@@ -46,7 +56,7 @@ The `implementer` agent is the specialist that writes all the code — it receiv
 
 ### 1. Parse
 
-- Read all task `*.md` files from TASKS_DIR (excluding files starting with `_`)
+- Read all task `*.md` files from `TASKS_DIR/todo/` (excluding files starting with `_`)
 - Read `_dependencies_table.md` — parse into a dependency graph (DAG)
 - Validate: no circular dependencies, all referenced dependencies exist
 
@@ -134,9 +144,13 @@ Track `auto_fix_attempts` count in the batch report for retrospective analysis.
 
 After the batch is committed and pushed, transition the ticket status of each task in the batch to **In Testing** via the configured work item tracker. If `tracker: local`, skip this step.
 
-### 13. Loop
+### 13. Archive Completed Tasks
 
-- Go back to step 2 until all tasks are done
+Move each completed task file from `TASKS_DIR/todo/` to `TASKS_DIR/done/`.
+
+### 14. Loop
+
+- Go back to step 2 until all tasks in `todo/` are done
 - When all tasks are complete, report final summary
 
 ## Batch Report Persistence