Update plugin driver documentation to reflect native plugin support

[devin-ai-integration]

Update plugin driver documentation to reflect native plugin support

Summary

The plugin driver system documentation was outdated, stating that native C/C++ plugins were "planned for future release" when the implementation already exists. This PR updates the documentation to accurately reflect the current state of the codebase.

Key changes:

• Updated README.md to document native plugins as "Supported" instead of "Planned"
• Fixed incorrect type comment in plugin_config.h (was 0 = native, 1 = python, should be 0 = python, 1 = native)
• Added critical documentation about native plugin args lifetime (must copy during init, pointer freed after)
• Updated Python import examples to use correct from shared import syntax
• Added SafeLoggingAccess to documented components
• Documented that cycle_start/cycle_end are reserved hooks (loaded but not currently invoked)
• Updated DEVELOPMENT.md plugin section with accurate lifecycle description

Review & Testing Checklist for Human

• Verify native plugin implementation works: Load the example plugin at plugins/native/examples/test_plugin.so and confirm init/start_loop/stop_loop/cleanup are called correctly
• Verify Python import path: Confirm from shared import SafeBufferAccess, safe_extract_runtime_args_from_capsule works in actual plugins
• Verify type mapping fix: Confirm that type=0 in plugins.conf means Python and type=1 means Native (check against actual runtime behavior)

Recommended test plan: Build and run the native plugin example using the Makefile at plugins/native/examples/, then configure it in plugins.conf with type=1 and verify it loads correctly when the runtime starts.

Notes

• The cycle_start and cycle_end hooks are documented as "reserved" because while the symbols are loaded via dlsym, they are not actually invoked anywhere in the runtime code
• The args lifetime documentation is critical for native plugin authors - storing the pointer instead of copying will cause use-after-free bugs

Link to Devin run: https://app.devin.ai/sessions/7bb7a40970384ea79ffea4adc955a73a
Requested by: Thiago Alves (@thiagoralves)

[devin-ai-integration]

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