Restrict deploy targets to .agents and .claude skill dirs

Remove $HOME/.cline/skills from the default deploy targets everywhere
(SKILL.md, deploy action, CLI help, Taskfiles), document what $HOME is
and how it is resolved, and restore the execute bit on the cli api
scripts (build.sh, scaffold.sh, validate.sh) so 'task build' works.

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

scripts/Taskfile.yml

@@ -41,7 +41,7 @@ tasks:
 
   deploy:
     desc: |
-      Deploy a skill into $HOME/.agents/skills, $HOME/.claude/skills and $HOME/.cline/skills (absolute paths).
+      Deploy a skill into $HOME/.agents/skills and $HOME/.claude/skills (absolute paths).
       Usage: task deploy -- --skill-dir="/absolute/path/to/skill" [--mode=symlink|copy] [--force]
     cmds:
       - task: cli:deploy