chore: Change task numbering to decimal.

Hex doesn't sort nicely in the file system.

.config/dot/.claude/tasks/0012-folders-fixed-target-mapping.md

@@ -1,6 +1,6 @@
 ---
 spec: dot-setup-folders
-blocked-by: 000b-folders-unconditional-merge
+blocked-by: 0011-folders-unconditional-merge
 ---
 
 ## What to build

.config/dot/CLAUDE.md

@@ -149,11 +149,6 @@ Tests live at `~/.config/dot/tests/dot.fish`, run with
   `$HOME/.claude/`. Writing to `$HOME/.claude/tasks/` instead of
   `~/.config/dot/.claude/tasks/` silently lands files in Claude Code's own
   global config dir instead of the project.
-- Task file numbers (`.claude/tasks/<NNNN>-<slug>.md`) are lowercase
-  **hexadecimal**, not decimal — per `~/.claude/skills/to-tasks/SKILL.md`.
-  After `0009` comes `000a`, not `0010`. A past task-breakdown session
-  ignored this and produced a decimal `0010`, which had to be renamed back
-  to `000a` once caught.
 - An agent's `Bash` tool runs commands through **zsh**, not fish, so the
   `dot` fish function (defined in `~/.config/fish/functions/dot.fish`) is
   not on that shell's autoload path. Typing `dot <subcommand>` there