Update to ArchLang

{
  "description": "Use when the user wants to change an existing ArchLang .arch floor plan, e.g. \"make the bedroom 1 m wider\", \"add a bathroom next to the hall\", \"move the front door to the south wall\", \"merge the kitchen into the living room\". Reads the plan's facts with the archlang CLI, makes the smallest edit that does the job, and re-verifies. Not for writing a plan from a brief (archlang-brief-to-plan).",
  "included_files": [],
  "name": "archlang-edit-plan",
  "skill_md_contents": "---\nname: archlang-edit-plan\ndescription: Use when the user wants to change an existing ArchLang .arch floor plan, e.g. \"make the bedroom 1 m wider\", \"add a bathroom next to the hall\", \"move the front door to the south wall\", \"merge the kitchen into the living room\". Reads the plan's facts with the archlang CLI, makes the smallest edit that does the job, and re-verifies. Not for writing a plan from a brief (archlang-brief-to-plan).\nlicense: MIT\ncompatibility: Needs a shell with Node 18+ and the archlang CLI (npx -y @chanmeng666/archlang@1.60.0, or npm i -g @chanmeng666/archlang@1.60.0 for a global archlang).\n---\n\n# Edit an existing plan\n\nChange a `.arch` file without breaking what already works.\nIf `archlang` is not on the path, write `npx -y @chanmeng666/archlang@1.60.0` in its place.\nNever run a bare `arch`: on Linux, macOS and Git Bash that name is the coreutils command.\n\nThis skill is a workflow, not a language reference. Run `archlang spec` for the language and\n`archlang <cmd> --help` for a command's flags.\n\n## Scope\n\n- Run the `archlang` CLI commands below and no other program.\n- Change the one `.arch` file the user asked you to edit (`plan.arch` below). If the user has not\n  named it, ask. Besides it, write only the drawing the CLI renders and the `.bak` copy that\n  `--backup` keeps.\n- The user's explicit instructions take priority over these steps.\n\n## Steps\n\n1. **Record the starting state.** Run `archlang validate plan.arch --json` and\n   `archlang describe plan.arch --select rooms,totals --json`. Keep both results: they are what you\n   compare against at the end. If the plan already has errors, tell the user before you edit.\n2. **Choose the locks, then check the edit.** Before you edit, list the ids the request does not\n   name: those are the locks. For a change to one top-level `let`, ask first, with nothing written:\n   `archlang impact plan.arch --set NAME=value --lock <ids> --json`. For any other edit, make it in a\n   copy `new.arch` and check it after: `archlang impact new.arch --against plan.arch --lock <ids>\n   --json`. Exit `2` with `E_LOCKED_ELEMENT_CHANGED` names a locked element the edit moves: change the\n   edit, not the lock. A lock names elements by the `id=` written in the source (an unnamed one is\n   refused with `E_LOCK_UNNAMED`).\n3. **Read only what the change touches.** `archlang describe plan.arch --room <ids> --json` returns\n   those rooms with the doors, windows and furniture that touch them.\n   `archlang describe plan.arch --select freedom --json` says which positions the author typed\n   (`absolute`) and which the compiler derives. Change a typed number; a derived one moves by\n   itself when the thing it depends on moves.\n4. **Read the language for the forms you will write.** `archlang spec`.\n5. **Make the smallest edit.** Change the statements the request names and leave the rest as they\n   are: same ids, same order, same comments. Do not reformat the file and do not rewrite\n   statements you were not asked to change. When a room changes size, check the walls, doors,\n   windows and neighbouring rooms that share its edges.\n6. **Compile.** `archlang compile plan.arch -o plan.svg --json`. If `ok` is false, preview the\n   mechanical fixes with `archlang fix plan.arch --dry-run --json` and read the diff before you apply\n   them with `archlang fix plan.arch --backup`.\n7. **Move furniture out of the way if needed.** If the edit pushed a piece into a wall, a doorway\n   or a door swing, `archlang repair plan.arch -o plan.arch` moves it. Read `unresolved` for the pieces\n   it could not move.\n8. **Verify the change and nothing else.** Run the two commands from step 1 again, and\n   the `impact` check from step 2 on the edited file. The rooms you meant to change differ as\n   intended. Every other room has the same area and the same connections. No diagnostic is new unless the request causes it; if one is, tell the user.\n9. **Refresh the sheet if the drawing grew.** `archlang finish plan.arch --dry-run --json` shows what\n   is missing. If it reports that the drawing no longer fits the authored `paper` or `scale`,\n   `archlang finish plan.arch --reissue` may replace those two statements and nothing else.\n\n## When another agent may edit the same file\n\nPass the file's current revision as `--expected-hash <hash>`, as in\n`archlang fix plan.arch --expected-hash <hash> --json`. The `--json` result of each command that\nrewrites the file (`fix`, `finish`, `repair -o plan.arch`, `fmt --write`) says which hash that is:\n`source_hash` is the file as the command read it, and `written_hash` the file once the command has\nwritten it. A result that hands you rewritten text instead (`repair --json`, a `--dry-run`, or the\nMCP `repair`, `fix` and `finish` tools) gives `output_hash`, the file's revision once you write that\ntext to it unchanged. `archlang fmt plan.arch --json` reports `source_hash` without writing. If the\nfile changed since, the command writes nothing and exits `4` with `E_STALE_SOURCE`: read the file\nagain, redo your edit on what is there now, and use the new hash. This narrows the window for a\nclash; it is not a lock.\n\n## Report to the user\n\n- The statements you changed, as a short diff.\n- Before and after for the facts the request is about (for example the room's area).\n- Any new warning, and whether the request causes it.\n\n## When something goes wrong\n\n- Exit code `2` is a fault in the source: read the diagnostic, do not retry unchanged. `3` is a\n  wrong flag: run `archlang <cmd> --help`.\n- `archlang explain <CODE> --json` explains a diagnostic code.\n- If the request needs a new door or window and you are unsure where it can go,\n  `archlang suggest plan.arch --json` returns candidates with the reason for each.\n"
}