feat: add /docs custom slash command for documentation lookup

Adds .claude/commands/docs.md — a project-level Claude Code slash
command that searches official Kopia, Docker, rclone, and backend
documentation on demand.

Usage: /docs <query>
  e.g. /docs kopia retention policies
       /docs docker inspect fields
       /docs rclone s3 backend

Also updates .gitignore: .claude/ → .claude/* to allow tracking
.claude/commands/ alongside the existing .claude/agent.md exception.

Co-authored-by: Claude Sonnet 4.6 <noreply@anthropic.com>

.claude/commands/docs.md

@@ -0,0 +1,44 @@
+# /docs — Documentation Lookup for Kopi-Docka
+
+Search the official documentation for Kopia, Docker, rclone, and storage backends.
+
+## Usage
+
+```
+/docs <query>
+/docs kopia retention policies
+/docs docker inspect fields
+/docs rclone s3 backend
+/docs b2 credentials
+```
+
+## Instructions
+
+You are helping a developer working on **kopi-docka**, a Python CLI wrapper around Kopia for Docker backup. Look up the query `$ARGUMENTS` in the relevant official documentation.
+
+**Step 1 — Identify which source(s) to search:**
+
+| Topic keywords | Primary source |
+|---|---|
+| kopia, snapshot, repository, policy, retention, maintenance, restore, connect, `kopia *` | https://kopia.io/docs/ |
+| kopia CLI flags, subcommands | https://kopia.io/docs/reference/command-line/common/ |
+| kopia policies / retention | https://kopia.io/docs/advanced/policies/ |
+| docker run, inspect, container, volume, network, compose | https://docs.docker.com/reference/ |
+| docker SDK, Engine API | https://docs.docker.com/engine/api/latest/ |
+| rclone, rclone backend, rclone config | https://rclone.org/docs/ |
+| s3, aws, minio | https://rclone.org/s3/ |
+| gcs, google cloud storage | https://rclone.org/googlecloudstorage/ |
+| azure blob | https://rclone.org/azureblob/ |
+| b2, backblaze | https://rclone.org/b2/ |
+| sftp, ssh | https://rclone.org/sftp/ |
+| tailscale | https://tailscale.com/kb/ |
+
+**Step 2 — Fetch and read the relevant page(s).** Use WebFetch to retrieve the documentation. If the first page doesn't fully answer the question, follow relevant links or try a WebSearch.
+
+**Step 3 — Answer concisely** with:
+- The exact CLI flags / API fields / config keys relevant to the query
+- Any gotchas or non-obvious behavior
+- A direct link to the source page
+- If applicable: how this affects kopi-docka code (e.g. which file/method calls this)
+
+Keep the answer focused. No need to summarize the entire page — only what's relevant to `$ARGUMENTS`.

.gitignore

@@ -39,11 +39,12 @@ MagicMock/
 # Local AI tooling (Claude / Codex)
 # Session state, caches, local-only artifacts
 ############################
-.claude/
+.claude/*
 .codex/
 
-# Allow committed agent rules (optional but recommended)
+# Allow committed agent rules and project commands
 !.claude/agent.md
+!.claude/commands/
 !.codex/agent.md
 
 ############################