refactor(agent/lsp): table-driven server registry, shared client/manager helpers, compact docs
- servers.py: per-language _root_*/_spawn_* functions collapsed into declarative
ServerDef entries built by _make_spec/_simple_spawn/_markers_root (-707 LOC)
- client.py: _write/_send_reply/_cancel_task helpers replace repeated
try/except blocks; handler dispatch tables for server->client requests
- manager.py: _broken_key unifies the (server_id, root) key derivation
- install.py/cli.py/eventlog.py/workspace.py/protocol.py/range_shift.py/
reporter.py: dedupe helpers (_find_binary, _link_into_bin, _run_installer,
_emit_once, _walk_up), drop dead log_no_server_configured, compact docs
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