Enhance GitHub PR comment experience

[lelia]

Summary

Overhauls the GitHub PR comment experience across all 4 scanner types with a shared, centralized helper architecture. All features are enabled by default and fully configurable via GHA inputs, CLI flags, or environment variables.

Adds

• Branded logo headers — Socket shield logo inline with each section title
• Clickable file/line links — File paths link directly to the exact LoC on GitHub (see screenshots)
• Collapsible sections — Findings grouped under expandable <details> with severity badges; critical auto-expands, non-critical auto-collapses
• Syntax highlighting — Language-aware code fencing (25+ languages)
• CVE links & CVSS scores — Vulnerability IDs auto-link to NVD with inline CVSS scores for CVE-based scanners (Socket Tier 1, Trivy).
  • NOTE: SAST and secrets findings surface rule IDs and code context; richer contextual linking for these scanner types is planned as a follow-up.
• Auto PR labels — Severity-based labels with auto-creation and color-coded badges, customizable names
• Centralized helper module (github_pr_helpers.py) — Shared utilities + wrap_pr_comment_section() wrapper for plug-and-play integration of future OSS tools
• 9 new action.yml inputs for feature toggles and label customization
• docs/github-pr-comment-guide.md — Feature guide with configuration reference, common configs, and extensibility docs
• Unit tests for the helper module

Changes

• All 4 formatter files refactored to use shared helpers, eliminating wrapper boilerplate
• github_pr_notifier.py extended with label management and idempotent section updates
• README.md streamlined to single canonical Quick Start; duplicate GHA snippets replaced with links to docs
• docs/github-action.md updated to @1.0.28 / checkout v6.0.2; PR section consolidated into dedicated guide
• Local install docs now cross-reference GitHub Actions as first-class CI/CD option
• .gitignore reorganized: fixed *.md negation order, removed duplicates, added section headers

Removes

• Redundant GHA workflow snippets duplicated across README and docs
• All stale @1.0.26 version references
• ~30 duplicate .gitignore entries

Screenshots

Before

After

Clickable links

Jump to LoC

refs: ASK-191