chore: bump version to 4.5.0

Bug fixes:
- Fix inverted pager detection logic (returned error instead of path)
- Fix repo.Clone ignoring destination directory parameter
- Fix sheet loading using append on pre-sized slices
- Clean up partial files on copy failure
- Trim whitespace from editor config

Security:
- Add path traversal protection for cheatsheet names

Performance:
- Move regex compilation outside search loop
- Replace string concatenation with strings.Join in search

Build:
- Remove go:generate; embed config and usage as string literals
- Parallelize release builds
- Add fuzz testing infrastructure

Testing:
- Improve test coverage from 38.9% to 50.2%
- Add fuzz tests for search, filter, tags, and validation

Documentation:
- Fix inaccurate code examples in HACKING.md
- Add missing --conf and --all options to man page
- Add ADRs for path traversal, env parsing, and search parallelization
- Update CONTRIBUTING.md to reflect project policy

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

doc/adr/README.md

@@ -0,0 +1,38 @@
+# Architecture Decision Records
+
+This directory contains Architecture Decision Records (ADRs) for the cheat project.
+
+## What is an ADR?
+
+An Architecture Decision Record captures an important architectural decision made along with its context and consequences. ADRs help us:
+
+- Document why decisions were made
+- Understand the context and trade-offs
+- Review decisions when requirements change
+- Onboard new contributors
+
+## ADR Format
+
+Each ADR follows this template:
+
+1. **Title**: ADR-NNN: Brief description
+2. **Date**: When the decision was made
+3. **Status**: Proposed, Accepted, Deprecated, Superseded
+4. **Context**: What prompted this decision?
+5. **Decision**: What did we decide to do?
+6. **Consequences**: What are the positive, negative, and neutral outcomes?
+
+## Index of ADRs
+
+| ADR | Title | Status | Date |
+|-----|-------|--------|------|
+| [001](001-path-traversal-protection.md) | Path Traversal Protection for Cheatsheet Names | Accepted | 2025-01-21 |
+| [002](002-environment-variable-parsing.md) | No Defensive Checks for Environment Variable Parsing | Accepted | 2025-01-21 |
+| [003](003-search-parallelization.md) | No Parallelization for Search Operations | Accepted | 2025-01-22 |
+
+## Creating a New ADR
+
+1. Copy the template from an existing ADR
+2. Use the next sequential number
+3. Fill in all sections
+4. Include the ADR alongside the commit implementing the decision