docs: use real ~/.claude/projects/ path in first-run help and README (#996)

The CLI help text and README told first-time users to mine from ~/chats/,
a path that doesn't exist on any machine. Real location where Claude
Code writes session JSONL is ~/.claude/projects/<escaped-project-path>/.

Updates three user-visible strings:
- mempalace/cli.py line 7 ("Two ways to ingest" block)
- mempalace/cli.py line 25 (Examples block)
- README.md line 58 (Quickstart)

Website guides (website/guide/mining.md, getting-started.md) still
reference ~/chats/ for ChatGPT/Slack export scenarios where that remains
a valid placeholder. Those can be a separate PR if the maintainers want
to tilt the website examples toward Claude Code specifically.

Fixes #996.

README.md

@@ -55,7 +55,7 @@ mempalace init ~/projects/myapp
 ```bash
 # Mine content into the palace
 mempalace mine ~/projects/myapp                    # project files
-mempalace mine ~/chats/ --mode convos              # conversation exports
+mempalace mine ~/.claude/projects/ --mode convos   # Claude Code sessions (scope with --wing per project)
 
 # Search
 mempalace search "why did we switch to GraphQL"