chore: Add PyPI package support for uvx/pip installation (#1764)

* Initial plan

* Add package structure and resource path utilities

- Created langbot/ package with __init__.py and __main__.py entry point
- Added paths utility to find frontend and resource files from package installation
- Updated config loading to use resource paths
- Updated frontend serving to use resource paths
- Added MANIFEST.in for package data inclusion
- Updated pyproject.toml with build system and entry points

Co-authored-by: RockChinQ <45992437+RockChinQ@users.noreply.github.com>

* Add PyPI publishing workflow and update license

- Created GitHub Actions workflow to build frontend and publish to PyPI
- Added license field to pyproject.toml to fix deprecation warning
- Updated .gitignore to exclude build artifacts
- Tested package building successfully

Co-authored-by: RockChinQ <45992437+RockChinQ@users.noreply.github.com>

* Add PyPI installation documentation

- Created PYPI_INSTALLATION.md with detailed installation and usage instructions
- Updated README.md to feature uvx/pip installation as recommended method
- Updated README_EN.md with same changes for English documentation

Co-authored-by: RockChinQ <45992437+RockChinQ@users.noreply.github.com>

* Address code review feedback

- Made package-data configuration more specific to langbot package only
- Improved path detection with caching to avoid repeated file I/O
- Removed sys.path searching which was incorrect for package data
- Removed interactive input() call for non-interactive environment compatibility
- Simplified error messages for version check

Co-authored-by: RockChinQ <45992437+RockChinQ@users.noreply.github.com>

* Fix code review issues

- Use specific exception types instead of bare except
- Fix misleading comments about directory levels
- Remove redundant existence check before makedirs with exist_ok=True
- Use context manager for file opening to ensure proper cleanup

Co-authored-by: RockChinQ <45992437+RockChinQ@users.noreply.github.com>

* Simplify package configuration and document behavioral differences

- Removed redundant package-data configuration, relying on MANIFEST.in
- Added documentation about behavioral differences between package and source installation
- Clarified that include-package-data=true uses MANIFEST.in for data files

Co-authored-by: RockChinQ <45992437+RockChinQ@users.noreply.github.com>

* chore: update pyproject.toml

* chore: try pack templates in langbot/

* chore: update

* chore: update

* chore: update

* chore: update

* chore: update

* chore: adjust dir structure

* chore: fix imports

* fix: read default-pipeline-config.json

* fix: read default-pipeline-config.json

* fix: tests

* ci: publish pypi

* chore: bump version 4.6.0-beta.1 for testing

* chore: add templates/**

* fix: send adapters and requesters icons

* chore: bump version 4.6.0b2 for testing

* chore: add platform field for docker-compose.yaml

---------

Co-authored-by: copilot-swe-agent[bot] <198982749+Copilot@users.noreply.github.com>
Co-authored-by: RockChinQ <45992437+RockChinQ@users.noreply.github.com>
Co-authored-by: Junyan Qin <rockchinq@gmail.com>

src/langbot/pkg/pipeline/msgtrun/msgtrun.py

@@ -0,0 +1,35 @@
+from __future__ import annotations
+
+from .. import stage, entities
+from . import truncator
+from ...utils import importutil
+import langbot_plugin.api.entities.builtin.pipeline.query as pipeline_query
+from . import truncators
+
+importutil.import_modules_in_pkg(truncators)
+
+
+@stage.stage_class('ConversationMessageTruncator')
+class ConversationMessageTruncator(stage.PipelineStage):
+    """Conversation message truncator
+
+    Used to truncate the conversation message chain to adapt to the LLM message length limit.
+    """
+
+    trun: truncator.Truncator
+
+    async def initialize(self, pipeline_config: dict):
+        use_method = 'round'
+
+        for trun in truncator.preregistered_truncators:
+            if trun.name == use_method:
+                self.trun = trun(self.ap)
+                break
+        else:
+            raise ValueError(f'Unknown truncator: {use_method}')
+
+    async def process(self, query: pipeline_query.Query, stage_inst_name: str) -> entities.StageProcessResult:
+        """处理"""
+        query = await self.trun.truncate(query)
+
+        return entities.StageProcessResult(result_type=entities.ResultType.CONTINUE, new_query=query)