feat: install Agnostic Prompt Standard (APS) v1.1.16 skill (#83)

- Add APS skill at .github/skills/agnostic-prompt-standard/
- Add APS agent at .github/agents/aps-v1.1.16.agent.md
- Add APS badge to README.md

Co-authored-by: Copilot <[email protected]>

Author: jsburckhardt

.github/agents/aps-v1.1.16.agent.md

@@ -0,0 +1,83 @@
+---
+name: agnostic-prompt-standard
+description: The reference framework to generate, compile, and lint greenfield prompts that conform to the Agnostic Prompt Standard (APS) v1.0.
+license: MIT
+metadata:
+  repository: "https://github.com/chris-buckley/agnostic-prompt-standard"
+  author: "Christopher Buckley"
+  co_authors: "Juan Burckhardt; Anastasiya Smirnova"
+  spec_version: "1.0"
+  framework_revision: "1.1.16"
+  last_updated: "2026-02-18"
+---
+
+# Agnostic Prompt Standard (APS) v1.0 — Skill Entry
+
+This `SKILL.md` is the **entrypoint** for the Agnostic Prompt Standard (APS) v1.0.
+
+- The APS **normative spec** is in `references/` (those documents define the standard).
+- Everything else in this repository is **supporting material** (examples, templates, platform adapters).
+
+## Normative spec (APS v1.0)
+
+1. [00 Structure](references/00-structure.md)
+2. [01 Vocabulary](references/01-vocabulary.md)
+3. [02 Linting and formatting](references/02-linting-and-formatting.md)
+4. [03 Agentic control](references/03-agentic-control.md)
+5. [04 Schemas and types](references/04-schemas-and-types.md)
+6. [05 Grammar](references/05-grammar.md)
+7. [06 Logging and privacy](references/06-logging-and-privacy.md)
+8. [07 Error taxonomy](references/07-error-taxonomy.md)
+
+## Skill layout
+
+- `SKILL.md` — this file (skill entrypoint).
+- `references/` — the APS v1.0 normative documents (this is what an LSP/linter should ingest).
+- `assets/` — reusable examples for `<format>` and `<constants>` blocks.
+  - `constants/` — example constants blocks.
+    - `constants-json-block-v1.0.0.example.md`
+    - `constants-text-block-v1.0.0.example.md`
+    - `constants-csv-block-v1.0.0.example.md`
+  - `formats/` — example format blocks.
+    - `format-code-changes-full-v1.0.0.example.md`
+    - `format-code-map-v1.0.0.example.md`
+    - `format-docs-index-v1.0.0.example.md`
+    - `format-error-v1.0.0.example.md`
+    - `format-hierarchical-outline-v1.0.0.example.md`
+    - `format-ideation-list-v1.0.0.example.md`
+    - `format-link-manifest-v1.0.0.example.md`
+    - `format-markdown-table-v1.0.0.example.md`
+    - `format-smeac-plan-v1.0.0.example.md`
+    - `format-table-api-coverage-v1.0.0.example.md`
+- `_template/` — minimal skill skeleton for scaffolding new skills.
+  - `SKILL.md` — stub entrypoint with placeholder frontmatter.
+  - `references/`, `assets/constants/`, `assets/formats/`, `processes/`, `scripts/`, `guides/` — empty placeholder directories.
+- `processes/` — executable APS process documents (skill-specific workflows).
+  - `build-skill.md` — process for building new APS-compliant skills.
+- `guides/` — reference documents for humans and agents.
+  - `skill-authoring-v1.0.0.guide.md` — skill authoring reference.
+- `platforms/` — **non-normative** platform adapters. Each platform has a single `adaptor.md` file.
+  - `README.md` — platforms overview and contract.
+  - `_template/` — skeleton for new platform adapters.
+    - `adaptor.md`
+  - `claude-code/` — Claude Code CLI adapter.
+    - `adaptor.md` — platform constants, tool registry, and format contracts.
+  - `opencode/` — OpenCode adapter.
+    - `adaptor.md` — platform constants.
+  - `vscode-copilot/` — VS Code + GitHub Copilot adapter.
+    - `adaptor.md` — platform constants, tool registry, and format contracts.
+- `scripts/` — optional build / compile / lint scripts (empty by default).
+
+---
+
+## Platform adapters
+
+Platform-specific details (file discovery, frontmatter dialects, tool naming) are documented in `platforms/`.
+
+→ See [platforms/README.md](platforms/README.md) for overview and how to add new adapters.
+
+### VS Code + GitHub Copilot
+
+The initial adapter for VS Code + GitHub Copilot is at `platforms/vscode-copilot/`.
+
+→ See [platforms/vscode-copilot/adaptor.md](platforms/vscode-copilot/adaptor.md) for platform constants, tool registry, and format contracts.

.github/skills/agnostic-prompt-standard/SKILL.md

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+---
+name: <skill-id>
+description: "<One-sentence skill description>"
+license: MIT
+metadata:
+  author: "<Your Name>"
+  spec_version: "1.0"
+  framework_revision: "1.0.0"
+  last_updated: "<YYYY-MM-DD>"
+---
+
+# <Skill Name>
+
+<One-paragraph skill overview: what it does, who it is for, and why it exists.>
+
+## References
+
+1. [00 <First reference>](references/00-<name>.md)
+
+## Skill layout
+
+- `SKILL.md` — this file (skill entrypoint).
+- `references/` — normative specification documents.
+- `assets/` — reusable constants and format contracts.
+  - `constants/` — constant blocks.
+  - `formats/` — format contracts.
+- `processes/` — executable APS process documents.
+- `guides/` — prose reference documents for humans and agents.
+- `scripts/` — optional build / compile / lint scripts.