chore: add shared skills catalog (19 skills), installers, manifest, validator

skills/documentation-and-adrs/SKILL.md

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+---
+name: documentation-and-adrs
+description: Use when documenting architectural decisions, drafting ADRs (Architecture Decision Records), or writing technical specifications and system documentation.
+---
+
+# Architecture Decision Records (ADRs) & Technical Documentation
+
+## Purpose
+Produce concise, actionable, and structured architectural documentation and ADRs that capture the context, options considered, and tradeoffs made.
+
+## ADR Standard Structure (MADR Format)
+
+```markdown
+# [Short title of solved problem and decision]
+
+* **Status:** proposed | accepted | rejected | deprecated | superseded
+* **Deciders:** [List of stakeholders/engineers]
+* **Date:** YYYY-MM-DD
+
+## Context and Problem Statement
+What problem are we solving? What are the constraints, requirements, and background context?
+
+## Decision Drivers
+* Driver 1 (e.g. performance under 50ms latency)
+* Driver 2 (e.g. zero external infrastructure dependencies)
+* Driver 3 (e.g. strict backwards compatibility)
+
+## Considered Options
+1. Option A — [Short description]
+2. Option B — [Short description]
+3. Option C — [Short description]
+
+## Decision Outcome
+Chosen option: "Option A", because [justification linking to drivers].
+
+### Positive Consequences
+* Clear benefit 1
+* Clear benefit 2
+
+### Negative Consequences / Tradeoffs
+* Accepted limitation 1
+* Migration cost or operational overhead
+
+## Pros and Cons of Options
+[Brief comparison table or bullet breakdown]
+```
+
+## Documentation Principles
+1. **One Home per Fact:** Do not duplicate invariants across multiple files.
+2. **Focus on "Why" and "Tradeoffs":** Code shows *how*; documentation must explain *why* this choice was made over alternatives.
+3. **No Fluff / Slop:** Direct, concise language. Omit generic platitudes.