[thekevinbot]

Drop the --include-default injection from the Python plugin launcher so a plugin adds its functions and nothing else. Nothing else used the hidden --include-default flag or default_records_table, so both are removed, along with the now-dead user_passed_config helper. Docs fixed in docs/reference/cli.md (Plugins) and docs/howto/write-a-plugin.md (Boundaries).

Fixes #1225

Changelog / Migrations

• Changelog fragment added under packages/{python,rust}/changelog.d/
• Migration fragment with the same slug added under packages/{python,rust}/migrations.d/

E2E Verification

• Ran e2e suites locally for every affected SDK
• Python SDK e2e: pass after merging main (Test one-level glob listings at speed of light #1317), receipt packages/python/e2e-attestations/claude-1225-plugin-no-default.json. Impacted files only (plugin launch / config path): plugin_discovery_test.py, plugin_extension_discovery_test.py, extension_package_test.py, cli_version_test.py, query_contract_test.py -- 19 passed
• TypeScript SDK e2e: pass (just e2e-attest-ts)
• Rust core: cargo test --features cli --workspace passes except watcher tests that fail only under inotify exhaustion from parallel agents (pass alone)
• packages/ts/e2e-attestations/claude-1225-plugin-no-default.json receipt written
• Command(s) run: testing-conventions e2e attest 'uv run python -m pytest tests/e2e/<impacted files> -x -q', just e2e-attest-ts
• Result summary: TS and Python receipts recorded.