Each channel message now shows the hash size its sender's path uses, read
from bits 7-6 of the path byte that the originator writes and repeaters keep.
The server sends it as path_hash_size (packetpath.HashSize); the frontend
helper pathHashSize() applies the same rule and returns 0 for unknown.
One rule on both pages: the packet detail Hash Size row and the hex
breakdown call pathHashSize() too, so a 0-hop flood message reports the
same size on Channels and on its packet page. A direct packet with no hops
left reports no size, matching cmd/server/decoder.go. The cases live in
test-fixtures/path-hash-size-cases.json, read by the Go and JS tests.
## Problem
Per-observation `path_json` disagrees with `raw_hex` path section for
TRACE packets.
**Reproducer:** packet `af081a2c41281b1e`, observer `lutin🏡`
- `path_json`: `["67","33","D6","33","67"]` (5 hops — from TRACE
payload)
- `raw_hex` path section: `30 2D 0D 23` (4 bytes — SNR values in header)
## Root Cause
`DecodePacket` correctly parses TRACE packets by replacing `path.Hops`
with hop IDs from the payload's `pathData` field (the actual route).
However, the header path bytes for TRACE packets contain **SNR values**
(one per completed hop), not hop IDs.
`BuildPacketData` used `decoded.Path.Hops` to build `path_json`, which
for TRACE packets contained the payload-derived hops — not the header
path bytes that `raw_hex` stores. This caused `path_json` and `raw_hex`
to describe completely different paths.
## Fix
- Added `DecodePathFromRawHex(rawHex)` — extracts header path hops
directly from raw hex bytes, independent of any TRACE payload
overwriting.
- `BuildPacketData` now calls `DecodePathFromRawHex(msg.Raw)` instead of
using `decoded.Path.Hops`, guaranteeing `path_json` always matches the
`raw_hex` path section.
## Tests (8 new)
**`DecodePathFromRawHex` unit tests:**
- hash_size 1, 2, 3, 4
- zero-hop direct packets
- transport route (4-byte transport codes before path)
**`BuildPacketData` integration tests:**
- TRACE packet: asserts path_json matches raw_hex header path (not
payload hops)
- Non-TRACE packet: asserts path_json matches raw_hex header path
All existing tests continue to pass (`go test ./...` for both ingestor
and server).
Fixes#886
---------
Co-authored-by: you <you@example.com>
Sylvain Rabot