Generic host/repo/branch-aware CD on adnanh/webhook

Replaces the per-project deploy scripts and self-contained webhook
receivers with one manifest-driven implementation that lives outside the
application repositories and can be updated independently of them.

First targets: domaindingo test and prod on s5.

ai-context/style/working-style.md

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+# Working Style Checklist
+
+Decision ladder before writing code or tooling (from [Ponytail](https://github.com/DietrichGebert/ponytail)):
+
+1. **Does this need to exist?** → No: skip it (YAGNI)
+2. **Already in this codebase?** → Reuse, don't rewrite
+3. **Stdlib does it?** → Use it
+4. **Native platform feature?** → Use it
+5. **Installed dependency?** → Use it
+6. **One line?** → One line
+7. **Only then:** the minimum that works
+
+Lazy about the solution, never about reading the problem first.
+
+## Math & Arithmetic
+
+For numeric calculations in shell scripts, pick the simplest rung:
+- Shell arithmetic `$(( ))` — fixed-width integers, one line
+- `bc` — arbitrary precision when needed
+- Python `python3 -c "print(...)"` — complex logic or exact precision
+- Always validate edge cases (overflow, division by zero)
+
+## Plain English
+
+Write in plain English for system administrators:
+- Prefer short, direct sentences.
+- Use concrete verbs: check, read, write, test, stop, ask.
+- Avoid management and policy terms such as leverage, align, facilitate, ensure, optimize, stakeholder, outcome, and workflow.
+- Say who should act and under which condition.
+- Keep necessary technical terms, but explain unfamiliar ones.
+- Remove repetition and text that does not change the action.
+- Preserve the exact meaning and all safety requirements.