docs: rewrite README, add LICENSE, remove outdated files

- Rewrite README.md with comprehensive documentation covering all
  features: compression engines, meta plugins, filter plugins, server
  mode, MCP integration, and configuration
- Add MIT LICENSE file
- Delete README.org (consolidated into README.md)
- Delete empty PLAN.md
- Update AGENTS.md with current build/test commands and conventions

Co-Authored-By: andrew/openrouter/hunter-alpha <noreply@opencode.ai>

AGENTS.md

@@ -37,16 +37,3 @@ TERM=dumb cargo build --features server  # With server feature
 - Tests in `src/tests/` mirroring `src/` structure; shared helpers in `src/tests/common/test_helpers.rs`
 - Key helpers: `create_temp_dir()`, `create_temp_db()`, `test_compression_engine()`
 - Test naming: `test_<feature>_<scenario>`
-
-## Procedures
-
-### Fix build problems
-
-1. `TERM=dumb cargo check`
-2. Read affected files, fix errors, preserve functionality, don't downgrade versions
-3. Prefer `write_file` for full file rewrites; repeat from step 1
-
-### Fix formatting
-
-1. `TERM=dumb cargo fmt`
-2. Continue with fix build problems procedure