Settings panel: Connection Information, with Copy

[addhumal]

Closes #102.

What it does

Adds a Connection Information group in the device's Settings panel, above Take the Tour, showing what the session runs on (refreshed with each second's link stats) and a Copy Connection Information button. Device only: no wire change, nothing sent to the Mac.

ConnectionInfo (pbxproj AD01/FD01) formats the rows and the copied text from what StreamClient already keeps (linkStats, route/remoteRoute, hostVersion/hostProtocol, and the running stream). A second without samples reads "–", never zero. Copy Connection Information writes to UIPasteboard.general with .localOnly and updates client.clipboardHandled so Universal Clipboard does not carry it to the Mac and the Paste on ‹Mac› chip never offers Sill's own diagnostic text back; the row reads Copied for 2 s.

Why

When troubleshooting a slow link or filing a bug report, the session's numbers are spread across the panel header, the route line, the Mac's log and the DEBUG-only HUD. Putting them in one read-only group with a one-tap copy makes every number available from a Release build without presenting a sheet over the stream:

Row	Example
Mac	Mac mini
Connection	Wi-Fi / Wired / Direct / through Tailscale
Picture	2880×1800 · 60 fps · 15 Mbps (or Not streaming)
Received	60 fps (or –)
Round trip	7 ms (worst 14 ms)
Frame age	9 ms (worst 22 ms)
Mac's Sill	0.5.1 (protocol 1) (or an older Sill or the command-line host)
This iPad / iPhone	Sill 0.5.1 (4) · iPadOS 27.0 · iPad16,9

Checks

• Tests/checks/connection-info: 22 checks covering every row, missing samples ("–"), older hosts without a version, and the copied text with its UTC timestamp. 12 of 12 mutants caught. Added to CI's mutants list and the checks README.
• Tests/checks/run-all.sh and swift build -c release pass with only the known warnings.
• Verified live on an iPad Air simulator (iOS 27.0) against SillHost --synthetic on loopback.

[Saffsanity]

From a pass over all the open pull requests (nothing is decided yet): this adds its group at the same spot in HostSettingsPanel.swift as #96 (between This iPad and Take the Tour), so the two need one agreed order, with the gap before Take the Tour settled at the same time. Since the clipboard sharing from #78 is on main now, Copy Connection Information should write with .localOnly, so the Paste on Mac chip does not offer Sill's own text back; the other overlaps (#66, #72, #73, #93, #94, #99, #107, #117) are the ci.yml mutants line, the checks README and adjacent project-file entries.

[addhumal]

Thanks. Pushed c75c45b (and merged main in b6c4e10): Copy Connection Information now writes to UIPasteboard.general with .localOnly and sets client.clipboardHandled = board.changeCount, so the Paste on ‹Mac› chip never offers Sill's own diagnostic text back, and the group has the same 8 pt gap before Take the Tour as #96.