Rename address segments to <group>.<daemon>.<keyword>

[mikelangmayr]

• "scope" was jargon that appears in no config file, and the parse error said "keyword must be ..", using "keyword" for the whole address and "name" for its last segment
• errors, help text, docstrings and the CLI/client docs now say ..; the middle segment is a daemon's peer_id and the last is what the system already calls a keyword
• local variables renamed to match, so the code reads the same as the messages; peer_id() and parse_keyword() are positional everywhere, so no caller changes
• trimmed qualified_peer_id's docstring, whose rationale belongs in the design doc
• verified the messages: "address must be .., got: hsfei" and "wildcards (%) are not allowed in or "; suite passes (30 tests, including the live-broker round trip)