ci: add agentic daily test improver

[nitrocode]

what

why

tests

references

[Copilot]

Pull request overview

Adds an “agentic” Daily Test Improver workflow definition intended to run on a schedule and via /test-assist to propose and maintain testing improvements for the repo.

Changes:

• Introduces .github/workflows/daily-test-improver.md containing the Test Improver’s configuration, task loop, and operating guidelines.
• Defines triggers (scheduled + slash command) and limits (safe-outputs, tools) for the assistant’s actions.

[Copilot]

This file is placed under .github/workflows/ but uses a .md extension and a non–GitHub Actions trigger format (on: schedule: daily, slash_command, etc.). GitHub Actions will ignore it, so the "daily test improver" CI job likely won’t run unless there is additional tooling/app wiring elsewhere in the repo. If the intent is to run on GitHub Actions, convert this into a .yml workflow with a proper on.schedule.cron and jobs/steps (or add the missing runner workflow that consumes this .md).

[Copilot]

permissions: read-all appears incompatible with the workflow’s stated capabilities (creating PRs/issues and adding comments). If this is meant to run with GITHUB_TOKEN, it will need the appropriate write scopes (e.g., pull-requests: write, issues: write, contents: write) while still keeping least-privilege.

Suggested change

	permissions: read-all
	permissions:
	contents: write
	pull-requests: write
	issues: write

[Copilot]

YAML frontmatter typically needs to start at the first line of the Markdown file. The leading Markdown heading (# https://...) before the initial --- may prevent frontmatter parsing by tools that expect it at the top. Consider moving the URL reference below the frontmatter (or into the description) so the file begins with ---.

Suggested change

	# https://github.com/githubnext/agentics/blob/main/workflows/daily-test-improver.md
	---
	description: |
	A testing-focused repository assistant that runs daily to improve test quality and coverage.
	Can also be triggered on-demand via '/test-assist <instructions>' to perform specific tasks.
	---
	description: |
	A testing-focused repository assistant that runs daily to improve test quality and coverage.
	Can also be triggered on-demand via '/test-assist <instructions>' to perform specific tasks.
	Source: https://github.com/githubnext/agentics/blob/main/workflows/daily-test-improver.md