feat: deploy AIM (AI Agent Instruction Modules)

Phase 0 of #120 — first PR of the v1.0.0 cycle.

- Add AGENTS.md, aim.config.json, and instructions/ with 12 AIM modules
  (agent-workflow, shorthand, git-workflow, testing, powershell, markdown,
  readme, github-cli, releases, contributing, update, repository-specific).
- Migrate CLAUDE.md content to instructions/repository-specific.instructions.md,
  keeping only repo-specific content (project layout, $PSBPreference internals,
  task dependency variables, naming conventions, build workflows, BuildHelpers
  env vars). Generic content covered by standard AIM modules was dropped to
  avoid duplication.
- Fix stale references during migration: version 0.7.3 -> 0.8.0; public
  function count 9 -> 12 (signing functions added in 0.8.0).
- Delete CLAUDE.md.

Docs/config-only — no module code changes. Tests still pass
(314 passed, 0 failed, 2 skipped — the skips are git-tagging tests that
expectedly skip on feature branches).

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

Author: tablackburn

AGENTS.md

@@ -0,0 +1,72 @@
+# AI Agent Instructions
+
+AI agents working in this repository must follow these instructions.
+
+Template Version: 0.8.13
+
+Last sync: 2026-05-15 (Update this date when syncing from the centralized repository)
+
+## Instructions for AI Agents
+
+AI agents **must**:
+
+1. **When deploying or updating this template, follow `instructions/update.instructions.md` and
+   update the Last sync date above.**
+
+2. **Read `instructions/agent-workflow.instructions.md` FIRST to determine which other instruction
+   files apply to your task.** Follow all applicable instructions before proceeding with work.
+
+3. **Check `aim.config.json`** for module configuration and external source settings.
+
+## Instruction Applicability Matrix
+
+Use this matrix to determine which instruction files to read based on your task:
+
+| Task Type                    | Required Instructions                  |
+| ---------------------------- | -------------------------------------- |
+| Any task                     | `agent-workflow.instructions.md`       |
+| Any code or documentation    | `shorthand.instructions.md`            |
+| Git operations               | `git-workflow.instructions.md`         |
+| Writing tests                | `testing.instructions.md`              |
+| PowerShell code              | `powershell.instructions.md`           |
+| Documentation                | `markdown.instructions.md`             |
+| README files                 | `readme.instructions.md`               |
+| GitHub CLI usage             | `github-cli.instructions.md`           |
+| Creating releases            | `releases.instructions.md`             |
+| Repository-specific work     | `repository-specific.instructions.md`  |
+| Updating instructions        | `update.instructions.md`               |
+| Contributing to upstream     | `contributing.instructions.md`         |
+
+## Available Instruction Files
+
+- `agent-workflow.instructions.md` - Pre-flight protocol and task workflow
+- `shorthand.instructions.md` - Avoid shorthand and abbreviations
+- `git-workflow.instructions.md` - Git branching, commits, and PR conventions
+- `testing.instructions.md` - Test writing best practices
+- `powershell.instructions.md` - PowerShell coding standards
+- `markdown.instructions.md` - Markdown formatting standards
+- `readme.instructions.md` - README maintenance guidelines
+- `github-cli.instructions.md` - GitHub CLI usage guidelines
+- `releases.instructions.md` - Release management guidelines
+- `repository-specific.instructions.md` - Repository-specific customizations
+- `update.instructions.md` - Procedures for updating instructions
+- `contributing.instructions.md` - Contributing improvements to upstream
+
+## Quick Reference
+
+### Before Starting Any Task
+
+1. Identify the task type from the matrix above
+2. Read all applicable instruction files
+3. Follow the guidelines when implementing
+
+### Best Practices
+
+- Follow existing patterns in the codebase
+- Keep solutions simple and focused
+- Only make changes that are directly requested
+- Follow language-specific guidelines
+
+## Repository-Specific Instructions
+
+See `instructions/repository-specific.instructions.md` for customizations specific to this repository.