fix: move pinning hint to diagnostics section

[danielmeppiel]

Summary

Moves the inline pinning tip from cluttering the package install tree into the ── Diagnostics ── section at the bottom, following the established CLI UX pattern.

Before

[checkmark] owner/repo
  └─ 2 prompts integrated
Installed 1 APM dependencies
Tip: Pin versions with #tag or #sha for reproducible installs (e.g. owner/repo#v1.0.0)

After

[checkmark] owner/repo
  └─ 2 prompts integrated
Installed 1 APM dependencies

── Diagnostics ──
  [i] 1 dependency has no pinned version -- pin with #tag or #sha to prevent drift

Changes

• diagnostics.py: Add CATEGORY_INFO with info() method and _render_info_group() renderer (blue [i] prefix, rendered last after all warnings/errors)
• install.py: Convert has_unpinned_deps bool → unpinned_count int; emit single aggregated diagnostics.info() with count and drift-focused message
• test_diagnostics.py: Add TestInfoCategory (3 tests for info collection, rendering, ordering)
• test_install_output.py: Remove TestUnpinnedDepsDetection (logic moved to diagnostics layer)

Testing

2451 tests pass. 2 pre-existing failures on main confirmed (run on clean main without changes):

• test_install_local_package_relative_path (integration)
• test_notion_npm_server_config_generation (codex docker args)

[Copilot]

Pull request overview

This PR adjusts APM’s CLI UX by moving the version-pinning guidance from the inline install output into the structured ── Diagnostics ── summary, aligning it with the existing “collect then render” diagnostics pattern.

Changes:

• Added a new diagnostics category info with collection + rendering support, rendered last in the summary.
• Switched install-time unpinned tracking from a boolean to a counter and emits a single aggregated info diagnostic.
• Updated unit tests by adding coverage for the new info diagnostics behavior and removing the old unpinned detection unit test.

Reviewed changes

Copilot reviewed 4 out of 4 changed files in this pull request and generated 5 comments.

File	Description
src/apm_cli/utils/diagnostics.py	Introduces CATEGORY_INFO, info() recording, and info rendering in render_summary() (last).
src/apm_cli/commands/install.py	Counts unpinned dependencies and emits a single aggregated diagnostics info message instead of an inline tip.
tests/unit/test_diagnostics.py	Adds tests for collecting/rendering info diagnostics (but ordering test is currently incomplete).
tests/unit/test_install_output.py	Removes the unit test class that previously validated “unpinned” detection via DependencyReference.reference.