[WIP] feat(pressure reconciler): Support no planner integration

[cbartz]

Applicable spec: ISD-244

Overview

Support using no planner in the pressure reconciler.

Rationale

Currently we need one planner deployment per Github organisation. For some organisations, that only require a fixed pool of runners, a planner integration is overkill. As we are going to drop the legacy reconcile in a future PR, we need to let the pressure reconciler support no planner integration.

Checklist

• The charm style guide was applied.
• The contributing guide was applied.
• The changes are compliant with ISD054 - Managing Charm Complexity
• The documentation for charmhub is updated.
• The PR is tagged with appropriate label (urgent, trivial, complex).
• The changelog is updated with changes that affects the users of the charm.
• The application version number is updated in github-runner-manager/pyproject.toml.

[Copilot]

Pull request overview

This PR extends the pressure reconciler to operate without a planner integration (using a configured minimum runner count as fallback/static pressure), and refactors the HTTP server endpoints to use RunnerManager directly.

Changes:

• Add RunnerInfo + RunnerManager.get_runner_info() for aggregated runner status reporting.
• Allow PressureReconciler to be built/run with planner_client=None and update unit tests accordingly.
• Refactor /runner/check and /runner/flush HTTP endpoints to call RunnerManager instead of RunnerScaler; bump package version and update changelog.

Reviewed changes

Copilot reviewed 9 out of 9 changed files in this pull request and generated 5 comments.

Show a summary per file

File	Description
github-runner-manager/src/github_runner_manager/manager/pressure_reconciler.py	Makes planner optional, adds no-planner branch in create loop, and exposes build_runner_manager.
github-runner-manager/src/github_runner_manager/manager/runner_manager.py	Introduces RunnerInfo and get_runner_info() aggregation on RunnerManager.
github-runner-manager/src/github_runner_manager/http_server.py	Switches HTTP endpoints from RunnerScaler to RunnerManager and adjusts response serialization.
github-runner-manager/src/github_runner_manager/cli.py	Builds a RunnerManager for the HTTP server and wires pressure reconciler threads conditionally.
github-runner-manager/tests/unit/test_http_server.py	Updates tests to mock/use RunnerManager directly.
github-runner-manager/tests/unit/manager/test_runner_manager.py	Adds unit tests for RunnerManager.get_runner_info().
github-runner-manager/tests/unit/manager/test_pressure_reconciler.py	Adds tests for no-planner behavior and build function behavior.
github-runner-manager/pyproject.toml	Bumps application version to 0.16.0.
docs/changelog.md	Documents no-planner support and HTTP endpoint refactor.

[Copilot]

Switching /runner/flush from RunnerScaler.flush() to RunnerManager.flush_runners() changes behavior: it no longer runs RunnerManager.cleanup() first and it no longer flushes reactive processes (which RunnerScaler.flush() did when reactive config is present). If this endpoint is still expected to fully flush a deployment in legacy/ reactive mode, consider either restoring the cleanup + reactive flush steps (e.g., by keeping RunnerScaler here or by passing a higher-level façade into the HTTP server).

Suggested change

	try:
	try:
	runner_manager.cleanup()

[cbartz]

The behaviour change is fine - we no longer support legacy/reactive mode