docs: Block the tickets that edit a file by the ticket that changes the form of the file

Co-Authored-By: Claude Sonnet 5.5 <[email protected]>

Author: codeguru42

docs/dev/planning.md

@@ -39,6 +39,7 @@ A blocked-by link is the GitHub link that says that one issue waits for another
 
 - The planning session links two issues when one issue needs the code or the docs that the other issue makes.
 - The planning session also links two issues that will likely edit the same file, so that they do not cause a merge conflict. Examples are `skills/tasker/SKILL.md`, `docs/config.md`, `package.json`, the configuration schema, `docs/dev/code-conventions.md`, and a provider file with its dev doc.
+- A ticket that changes the form or the layout of a file goes early in its chain. Each open ticket that edits that file is blocked by it, also a ticket of a later milestone, so that each of them writes the new form. This bullet gives the direction of the link of the bullet before it. The bullet "An issue of an earlier milestone never waits ..." wins for a ticket of an earlier milestone. A ticket of a later milestone gets this link also when it waits for the last issue of a chain. Before the planning session adds a blocked-by link to an open issue, it runs `tasker status`. The issue is in flight when the output lists a task for it. The planning session adds no link to an issue in flight, because the task already builds on the old form. The planning session tells the operator, and the orchestrator of the task decides what the ticket does with the change.
 - An edit of a file under `test/helpers/` alone gets no blocked-by link.
 - Before the planning session drafts the issues of a milestone, it makes a table of the needs and the likely files of each issue. It adds the links from the table when it posts the issues, after the operator approves the drafts.
 - A line of tickets that edit one provider and its dev doc is one chain. A ticket with its own folder runs in parallel and gets a blocked-by link only for a real need.