Contribution guidelines for users and developers

[tomasz-placeholder]

What changed

New file: CONTRIBUTING.md

Two-track guide — one for non-coders (bug reports, feature ideas, translation edits via Poedit, browser-based doc fixes) and one for developers (setup, test commands, code conventions, PR workflow, files that must not be touched in regular PRs). Linked from the new Contributing section at the bottom of README.md.

README.md

• Version bump v1.3.1 → v1.3.5; "What's new" section rewritten to cover v1.3.2–v1.3.5 as a changelog list (auto-update safety, Aider setup wizard, sudo cache, sudo fixes) plus a note on post-tag master additions (task reorder, License v1.1)
• aider_setup_wizard added to the CLI tools list in sync_install.sh description, step 5 of the installer, and the tools/ tree diagram
• Git panel, Files tab, keyboard shortcut table: "Claude Code tabs" → "AI tabs" (provider-agnostic)
• claude_sessions.json → ai_sessions.json (schema R4.2, with migration note)
• tasks move added to the CLI examples block; Tasks panel description updated with reorder buttons and CLI-only project visibility
• Requirements section split: Claude Code marked as Claude-provider-specific; Copilot CLI / Aider added as optional alternatives
• Test count in prose replaced with ./tools/test_all.sh live output reference (previously stale hardcoded numbers)

defaults/license/LICENSE.*.md (all 13 languages)

Tomasz Frankowski (tomaszfrankowski@icloud.com) added as co-author in three locations per file: copyright line, contact block (§ header), attribution requirement list (§2), and the Owner section (§6)