docs: create provider-agnostic configuration guide for force multiplier architecture

## Summary

Document our advanced provider-agnostic configuration architecture that enables force multiplication across repositories and AI providers. This guide will help teams understand and adopt our 3/4 provider-agnostic approach.

## Background

From issue #904's analysis, we've achieved provider-agnostic implementations for:
- ✅ **Memory** via `knowledge/` directory
- ✅ **Slash Commands** via `commands/templates/`
- ✅ **MCP Servers** via standard protocol
- ❌ **Permissions** (Claude-specific)

This architecture creates network effects where improvements in dotfiles automatically benefit all projects.

## Deliverables

### 1. Create `docs/provider-agnostic-configuration.md`

**Structure:**
```markdown
# Provider-Agnostic Configuration Architecture

## Overview
- Force multiplier philosophy
- 3/4 provider-agnostic score
- Network effect benefits

## Memory Configuration
- How `knowledge/` works
- Provider implementations:
- Claude Code: `--add-dir knowledge/`
- Amazon Q: `~/.amazonq/rules/` symlink
- Cursor: [implementation details]
- Copilot: [implementation details]
- Migration guide from CLAUDE.md/.cursorrules.md

## Slash Commands
- Universal templates in `commands/templates/`
- Provider adapters:
- Claude Code: symlink to `.claude/commands/`
- Amazon Q: [implementation details]
- Others: [implementation details]
- Command generation process

## MCP Servers
- Standard protocol benefits
- Provider support matrix
- Configuration examples

## Permissions (Provider-Specific)
- Current Claude-specific approach
- Future provider-agnostic considerations
- Migration strategies

## Implementation Checklist
- Step-by-step setup guide
- Testing procedures
- Troubleshooting
```

### 2. Update existing documentation

**Files to update:**
- `README.md` - Add "Provider-Agnostic Configuration" section
- `docs/ai-provider-agnostic-context.md` - Reference new guide
- `CLAUDE.md` - Clarify relationship to universal `knowledge/`

### 3. Create provider comparison matrix

**Location:** `docs/provider-comparison-matrix.md`

Show which providers support which configuration categories and how to implement each.

## Success Criteria

- [ ] `docs/provider-agnostic-configuration.md` created with all sections
- [ ] Migration guides for each provider included
- [ ] README.md updated with provider-agnostic section
- [ ] Existing docs cross-referenced appropriately
- [ ] Provider comparison matrix created
- [ ] Examples show real implementations from dotfiles
- [ ] Clear actionable steps for teams to adopt

## Technical Notes

- Use actual file paths and code examples from our implementation
- Include both the "why" (force multiplier) and "how" (technical steps)
- Reference specific commits/PRs where these patterns were established
- Document lessons learned from the evolution (e.g., why `knowledge/` > `CLAUDE.md`)

## Related

- Issue #904: Force multiplier configuration analysis
- Issue #903: Original configuration matrix spike
- PR #892: Permission improvements
- Principle: systems-stewardship
- Principle: versioning-mindset

## Labels

- documentation
- enhancement
- provider-agnostic
- force-multiplier
- good first issue

Start by reading issue #904, issue #903, and the existing docs/ai-provider-agnostic-context.md, README.md, and CLAUDE.md. Inspect the knowledge/ and commands/templates/ directories and related provider implementations before drafting the two new guides. Done means all listed sections, provider migration details, cross-references, examples, and the comparison matrix are present.

Written by the indexing model from the issue text.