Migrate to native db.* API; drop subprocess shelling

Replace sqlite3 process_run shelling with Pact 0.13's native db.open/
db.exec/db.query/db.query_one API. Eliminates temp file creation,
JSON parsing boilerplate (jstr/jint/is_empty_json), and all subprocess
overhead.

Updates br:next slash command with --json flag usage and improved
parallel execution guidance.

Author: nhumrich

commands/br-next.md

@@ -6,10 +6,10 @@ Run `git rev-parse --show-toplevel` to get the repo basename. If in a git repo,
 
 ## 2. Fetch ready tasks
 
-- In a repo: `br ready -t repo:<basename>`
-- Not in a repo: `br ready`
+- In a repo: `br ready -t repo:<basename> --json`
+- Not in a repo: `br ready --json`
 
-If no tasks are ready, run `br blocked`, report what's stuck, and ask the user how to proceed.
+If no tasks are ready, run `br blocked --json`, report what's stuck, and ask the user how to proceed.
 
 ## 3. Rank and select (up to 5)
 
@@ -20,11 +20,26 @@ From the ready list, pick the best tasks to work on now:
 3. **Unblocks others** — if you can tell a task is a dependency for blocked work, prefer it
 4. **Skip vague/unclear tasks** — if a task title is ambiguous, deprioritize it
 
-Select up to 5 tasks. If only 1 is ready, just pick it.
+Create an implementation plan:
+* Select up to 5 tasks. If only 1 is ready, just pick it.
+* Identify which can be done in true parallel (e.g. multiple agents, parallel file edits)
+* Note any logical sequencing needed
+
 
 ## 4. Start and execute
 
 - Run `br start <id>` for each selected task
 - If 1 task: begin implementation directly
 - If 2+ tasks: use the `dispatching-parallel-agents` skill to work them in parallel (each agent gets a worktree)
 - Tell the user which tasks you're picking up and why
+- execute the plan from above
+- As each task is completed:
+  * verify the implementation works
+  * run /simplify on the solution
+  * close the task: `br close <id>`
+- show the final summary
+
+## Best practices:
+- Use parallel file edits when tasks touch different files
+- Update br task status immediately before starting and after completing each task
+- If a task fails, leave it in_progress and report the issue to the user, and also note it by using `br edit --append`