[MeshCore P3] M2 - Resolution spike (path_hash_mode / path_update / trace_data) [decision gate]

[pskillen]

Parent

Part of #267. Milestone M2 of the passive packet path subsystem. Decision gate for M3+.

Design: ADR-0001 docs/features/meshcore/packet-path-tracing/adr/

Goal

Prove or disprove a safe hash → identity binding before building enrichment.

Scope

• Investigate path_hash_mode semantics (does it change segment interpretation / identity key?).
• Investigate whether path_update (pubkey-only in captures today) and trace_data can bind a segment to a node.
• Decide centrality compute location: Postgres vs Neo4j.
• Update traceroute ADR-0001 and packet-path ADR-0001 with findings + decisions.

Acceptance criteria

• Written outcome: proven rule (with algorithm) or documented "unproven, stay hash-only".
• path_hash_mode and centrality-location decisions recorded in the ADR.

Out of scope

• Any production matcher (that is M3, only if this spike yields a proven rule). No suffix/prefix/recency heuristics.