chore: refactor vm health [DO NOT MERGE WITHOUT CHANGING BASE TO MAIN]

[yanksyoon]

DO NOT MERGE WITHOUT CHANGING BASE TO MAIN

Applicable spec:

Overview

• Remove VM Health information from VM dataclass
• Calculate health from RunnerInstance

Rationale

• VM's health attribute was a mutating property. Remove the mutation.
• RunnerInstance's health is also a mutating property. Remove the mutation.

Juju Events Changes

Module Changes

Library Changes

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.

No user facing changes.

[yanksyoon]

Review help comments

[github-actions]

TICS Quality Gate

❌ Failed

The following errors have occurred during analysis:

❌ [ERROR 5333] Project database 'github-runner-operator' already is connected to a started TICSQServer process that has not registered a stop time. To avoid data corruption, analysis is aborted. Details of the other TICSQServer process: started at 2025-07-09 14:32:08.000 by user ubuntu.

.github/workflows/tics.yaml / TICS / TICS GitHub Action