Add layered environment model and taskfile composition rules

Fold two overlapping local skills (scripts-shell, shell-scripts-module)
into this one, keeping only what it did not already cover.

- Add references/environment-model.md: the three-layer .env selector model,
  why set -a dot-sourcing beats export $(grep|xargs), tracked samples, the
  no-re-sourcing rule for module readers, and the deployment boundary
  (repo-presence is not git-tracked is not deployed).
- Extend references/taskfile.md with the one-env-driven-task rule (no
  :default pairs) and composing commands through the task surface.
- Add the lifecycle-hook module type to references/module-patterns.md.
- Keep this skill's _moduleExampleV1_ naming as canonical; the retired
  skills' HL_V1_ and double-underscore dialects were not carried over.

Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>

README.md

@@ -14,7 +14,8 @@ development-scripts/
 │   ├── shared-modules.md             # loggers and base, and the logging bootstrap rule
 │   ├── taskfile.md                   # Module and root Taskfile integration
 │   ├── workflows.md                  # Create, change, validate
-│   └── module-patterns.md            # Module type and dependency decision guide
+│   ├── module-patterns.md            # Module type and dependency decision guide
+│   └── environment-model.md          # Layered .env model, samples, shipping into a target repo
 └── assets/
     ├── module-example-v1/            # Scaffold to copy for a new module
     ├── loggers/                      # Working reference implementation