[gunicsba]

Summary

Closes #94.

An implement used to stay in manual mode after connecting until someone pressed AOG's ISOBUS SC button. With this change the TC switches section control on by itself.

• The TC remembers the section control state it wants. At startup that comes from a new settings.json key, sectionControlOnConnect, which defaults to true.
• 2 s after a client's object pool is activated, the TC applies that state. It sets its local auto flag, so AOG's section states (PGN 229) are forwarded, and it writes DDI 160 (Section Control State) if the implement declares it.
• Every activation starts with a fresh ClientState, so this also covers implements that connect after startup, reconnects and pool re-uploads.
• AOG's SC button works as before: PGN 241 switches every connected client. It now also sets the state used for implements that connect later.
• The implement keeps the final say. If it declines, or the operator switches it back to manual, its DDI 160 report is followed as before.

AOG only sends PGN 241 when the button is pressed, and the button shows the state from the TC heartbeat. That means AOG doesn't override the default, and its button shows ON once the implement is switched on.

Switching on when AOG opens a field

A second setting, sectionControlOnFieldOpen (default true), does the same thing when AOG opens a field: the TC calls the same code as PGN 241 "enabled", as if the SC button had been pressed.

• AOG sends the field name (PGN 0xF3) on every field open and close, and again when the TC reconnects. A non-empty name counts as a field opening.
• Older AOG versions don't send the field name. For those, PGN 229 starting after a 2 s gap counts as a field opening, because AOG only sends PGN 229 while a field is open.
• Both signals report the same opening, so the TC acts on it at most once per 5 s.
• Field open and close are logged as [Field] AOG opened field '...' and [Field] AOG closed the field.

Background: in a field log from 2026-10-13, after field changes a spreader in automatic spread full width without receiving setpoints (see #106). This option makes a field change restart automatic section control in the TC without anyone pressing the button.

Notes

• Track control (DDI 515) is not switched on automatically. It is still only driven by the AOG button.
• To turn these off, set "sectionControlOnConnect": false or "sectionControlOnFieldOpen": false in settings.json. Both are listed in the readme. There is no VT Config toggle yet.
• Announce guidance track data (DDI 507-511, 513) to implements #84 also handles PGN 0xF3; whichever lands second should merge the two handlers.

Testing

• Release build passes on Windows (MSVC).
• Not yet tested on a real implement. Things to check: the log shows [TC] Applying initial section control state: enabled about 2 s after the pool is activated, the implement reports DDI 160 = 1, and AOG's button shows ON.

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