Add GP4-GP6 guest ports and per-port 24V sensing for X7

[follesoe]

Summary

As part of X7, the platform will have 6 guest ports (up from 3). This PR extends the guest port definitions to GP4–GP6 in protobuf_definitions/message_formats.proto, adds per-port 24V and 5V current sensing for all six ports, and renames the 20V fields to 24V.

Location	Change
GuestPortNumber enum	Added GUEST_PORT_NUMBER_PORT_4..6 (values 4–6)
GuestPortInfo	Added gp4..gp6 (fields 4–6)
GuestPortCurrent	Added gp4_bat..gp6_bat (fields 5–7), per-port gp1_24v..gp6_24v (fields 8–13), and per-port gp1_5v..gp6_5v (fields 14–19)
ErrorFlags	Added per-port flags for GP4–GP6 (read, not_flashed, unknown_device, device_connection, device, bat_current), per-port gp1_24v_current..gp6_24v_current, and per-port gp1_5v_current..gp6_5v_current — new field numbers 48–77
Blueye.Protocol.Protobuf.csproj	Version bump 5.9.0 → 6.0.0

Current sensing

X7 adds per-port 24V and 5V current sensing to all six guest ports:

• GuestPortCurrent gains gp1_24v–gp6_24v (fields 8–13) and gp1_5v–gp6_5v (fields 14–19). The existing common-supply field is kept for backwards compatibility (field 4) and is now documented as the common/input 24V supply.
• ErrorFlags gains per-port gp1_24v_current–gp6_24v_current (fields 66–71) and gp1_5v_current–gp6_5v_current (fields 72–77), alongside the existing common gp_24v_current.

Naming: 20V → 24V

The guest-port supply is 24V, so the 20V fields are renamed: gp_20v → gp_24v, gp_20v_current → gp_24v_current. Field numbers and types are unchanged, so the wire format stays compatible — only the generated symbol names change (a source-level breaking change for consumers, intentional). This follows the review discussion concluding on 24V.

ErrorFlags ordering

The new per-port flags are grouped so that gp1..gp6 of each error type are listed together (e.g. all *_read, then all *_not_flashed, …). The existing GP1–GP3 flags keep their original field numbers (9–41) for wire compatibility; the new flags use 48–77, assigned so they read in ascending order down the file. As a result gp_24v_current (field 42) now appears later in source than gp6_bat_current (65) — proto does not require numeric source order.

Design notes

• Wire compatibility preserved. No existing field number changed; only field names (20V→24V) and source ordering were modified.
• Comment consistency. All per-port bat_current / 24v_current / 5v_current comments use the "guest port N" full-name form, matching the other per-port flags (this also corrected the pre-existing GP1–GP3 lines).

Validation

• protolint passes
• protoc compiles cleanly
• ErrorFlags field numbers verified unique and contiguous (1–77); GuestPortCurrent (1–19)

Downstream note

The generated consumer libraries (C++ / Python / TS / C#) and firmware will need to handle the new fields and the 20V→24V renames, but those live outside this repo. Tracked for libguestport in BluEye-Robotics/libguestport#371.

🤖 Generated with Claude Code

[jp-pino]

We also have 5V current sensing and fault detection per GP

[jp-pino]

LGTM