docs(agents): park #62 Engine NO_HOLE; fix stale #47 cite

[AdamRickards]

Docs-only park update from current main (c2fd150).

• Adds the get_interface_statistics: SSH counters omit cpu/vlan rows (mops/snmp n=36 vs ssh 28) #272 get_interface_statistics Engine NO_HOLE row (accepted 2026-09-13): index_filter only applies on writes; physical-only read parity needs a read-side filter in Engine.
• Adds the get_rstp_port.read: SSH parse n=0 (cli listed; hang-open cleared post-#215) #62 get_rstp_port Engine NO_HOLE row: per-port CLI-only fields, unbound dict-read index, and HARD iterate_from fanout timeout.
• Marks the existing get_interfaces.read: snmp call-budget-fanout (18 OID walks; phase=call) #47 get_interfaces SNMP fanout reference closed.
• Supersedes stale PR docs(agents): park #272 egress physical-filter NO_HOLE #276, whose pre-scrub diff is not mergeable; Architect can close docs(agents): park #272 egress physical-filter NO_HOLE #276.

Related: #272 #62