refactor(implement): update SKILL and batching algorithm for sequential task execution

- Changed the implementation strategy to execute tasks sequentially instead of in parallel, enhancing clarity and control.
- Updated documentation to reflect the new execution model, emphasizing dependency-aware batching and integrated code review.
- Revised the batching algorithm to ensure tasks are grouped for review while maintaining sequential execution within each batch.
- Removed references to parallel subagents and adjusted task ownership checks accordingly.

This refactor aims to streamline the implementation process and improve the overall workflow.

.claude/commands/implement/references/batching-algorithm.md

@@ -3,29 +3,31 @@
 ## Topological Sort with Batch Grouping
 
 The `/implement` skill uses a topological sort to determine execution order,
-then groups tasks into batches for parallel execution.
+then groups tasks into batches for code review and commit. Execution within a
+batch is **sequential** — no subagents, no parallelism.
 
 ## Algorithm
 
 1. Build adjacency list from `_dependencies_table.md`
 2. Compute in-degree for each task node
-3. Initialize batch 0 with all nodes that have in-degree 0
+3. Initialize the ready set with all nodes that have in-degree 0
 4. For each batch:
-   a. Select up to 4 tasks from the ready set
-   b. Check file ownership — if two tasks would write the same file, defer one to the next batch
-   c. Launch selected tasks as parallel implementer subagents
-   d. When all complete, remove them from the graph and decrement in-degrees of dependents
-   e. Add newly zero-in-degree nodes to the next batch's ready set
+   a. Select up to 4 tasks from the ready set (default batch size cap)
+   b. Implement the selected tasks one at a time in topological order
+   c. When all tasks in the batch complete, remove them from the graph and
+      decrement in-degrees of dependents
+   d. Add newly zero-in-degree nodes to the ready set
 5. Repeat until the graph is empty
 
-## File Ownership Conflict Resolution
+## Ordering Inside a Batch
 
-When two tasks in the same batch map to overlapping files:
-- Prefer to run the lower-numbered task first (it's more foundational)
-- Defer the higher-numbered task to the next batch
-- If both have equal priority, ask the user
+Tasks inside a batch are executed in topological order — a task is only
+started after every task it depends on (inside the batch or in a previous
+batch) is done. When two tasks have the same topological rank, prefer the
+lower-numbered (more foundational) task first.
 
 ## Complexity Budget
 
 Each batch should not exceed 20 total complexity points.
 If it does, split the batch and let the user choose which tasks to include.
+The budget exists to keep the per-batch code review scope reviewable.