Add connected COC Map Hub preview

[EthanOConnor]

What

• adds the connected Map Hub workflow, credentials, first-use connection, venue/event-oriented browsing, managed workspaces, and assignment-safe behavior
• carries the modern tiled imagery stack used by the Kelsey Creek/Wilburton workflow
• integrates the bounded viewport scheduler from Bound tiled raster viewport admission #1 with the shared raster resource manager
• completes the missing folder/image/info/warning action resources that caused debug builds to abort
• makes the native credential backends portable across macOS, Windows, Android, and Linux
• fixes Windows KMZ staging-file ownership during export

Why

This is the distributable COC preview line: Mapper can connect directly to the map library, browse by venue and event, and open managed work without requiring users to configure settings first. It also includes the tiled-source convergence fix needed for large aerial sources.

Checks

• exact commit: 86b1bf9
• GitHub Actions: macOS, Windows, Linux, and Android all successful
• local macOS suite: 49/49 passed
• targeted map_printer_t after KMZ fix: passed
• focused tiled-raster suite: 10/10 passed
• published macOS DMG passed the Actions startup smoke and local hdiutil verification
• published DMG SHA-256: cd17c2bd5cb1a174cc2752f1f19a8954af8d33702e5c212b65a160a3b3255701

Public preview: https://github.com/EthanOConnor/mapper-coc/releases/tag/map-hub-preview-2026-07-18

This remains a draft while the COC workflow is evaluated and before the broader feature line is decomposed for upstream-quality review.