docs: add coding guidelines and copilot instructions

[microsasa]

Summary

Adds coding guidelines and wires them into the entire agent pipeline.

New files

• .github/CODING_GUIDELINES.md — coding standards for all contributors: type safety (pyright strict, no duck typing, no getattr/hasattr, no assert for validation, TYPE_CHECKING banned), data modelling (Pydantic for JSON/API, Click for CLI, frozen dataclasses internally), error handling, logging (loguru), testing, security, formatting.
• .github/copilot-instructions.md — pointer to the guidelines file. Copilot code review reads this automatically and follows the link (verified empirically on PRs test: verify Copilot reads copilot-instructions.md from PR branch #478 and test: verify Copilot follows guidelines link (clean retest) #479).

Agent workflow updates

All 6 agent workflows now read and follow the guidelines:

• issue-implementer.md — write code following guidelines
• review-responder.md — fix review comments following guidelines
• ci-fixer.md — don't introduce violations while fixing CI
• quality-gate.md — verify compliance as part of merge evaluation
• code-health.md — flag violations in existing code on main
• test-analysis.md — context for coding standards

Code changes

• logging_config.py — removed TYPE_CHECKING guard, replaced with runtime import loguru + string annotation (complies with new ban)
• pyproject.toml — removed stale if TYPE_CHECKING: coverage exclusion
• architecture.md / changelog.md — updated stale TYPE_CHECKING references

How it works

No new workflow needed. The existing pipeline handles everything:

1. Implementer writes code following guidelines
2. Copilot code review flags violations as review comments
3. Orchestrator dispatches responder to fix violations
4. Quality gate verifies compliance before merge
5. Code-health finds violations in existing code on main

Closes #110

[Copilot]

Pull request overview

Adds repository-wide coding standards and ensures the agent workflows (and Copilot) explicitly read/follow them, while updating a small bit of code/docs to comply with the new TYPE_CHECKING ban.

Changes:

• Add .github/CODING_GUIDELINES.md and .github/copilot-instructions.md to standardize contributor/agent behavior.
• Update all agent workflow instruction files to reference the coding guidelines.
• Remove TYPE_CHECKING-based typing import usage and related stale references (plus coverage exclusion cleanup).

Reviewed changes

Copilot reviewed 12 out of 12 changed files in this pull request and generated 1 comment.

Show a summary per file

File	Description
src/copilot_usage/logging_config.py	Removes TYPE_CHECKING guard and adds runtime import loguru to support loguru.Record annotation usage.
src/copilot_usage/docs/changelog.md	Updates changelog entry to reflect the new logging import approach.
src/copilot_usage/docs/architecture.md	Updates component documentation to reflect runtime loguru import approach.
pyproject.toml	Removes coverage exclusion line for if TYPE_CHECKING:.
.github/workflows/test-analysis.md	Instructs agent to read coding guidelines for standards context.
.github/workflows/review-responder.md	Requires coding guideline compliance when addressing review comments.
.github/workflows/quality-gate.md	Adds explicit guideline compliance verification step.
.github/workflows/issue-implementer.md	Requires implementer to follow coding guidelines for all authored code.
.github/workflows/code-health.md	Uses coding guidelines as the standard for flagging cleanup items.
.github/workflows/ci-fixer.md	Requires coding guideline compliance when fixing CI.
.github/copilot-instructions.md	Adds Copilot instruction pointer to the coding guidelines + repo layout overview.
.github/CODING_GUIDELINES.md	Introduces repo-wide coding standards (typing, imports, error handling, testing, security, formatting).

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