Update README and in-app User Guide for VNC, Import/Export, and connect-time prompting

Both docs still described VNC as unimplemented and required usernames
up front for SSH/RDP -- neither has been true for a while. Brings them
in line with the actual current feature set: VNC's encodings/clipboard/
cursor sync/display modes and honest Apple Screen Sharing auth status,
blank-username connect-time prompting across all three protocols,
profile Import/Export and mRemoteNG import, and the new prompt
visibility behavior (issue #22). docs/USER_GUIDE.md also drives the
in-app Help -> User Guide dialog and the PDF shipped with releases.

Bump version to v2026.9.16.7.

Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>

README.md

@@ -15,16 +15,23 @@ OrbitHub is in active development.
 
 - Milestones completed: M0-M9
 - Current milestone: Milestone 10 (v1.0 Stabilization)
-- Latest checkpoint tag: `v2026.9.15`
-- VNC (M6) covers standard VNC Authentication and no-auth servers; see
-  [docs/PROGRESS.md](docs/PROGRESS.md) for known gaps (Apple Screen
-  Sharing auth, compression encodings, resize, cursor sync, clipboard)
+- Latest published release: `v2026.9.16`; a `v2026.9.16.6` release is
+  drafted with several post-`.16` fixes and is pending a macOS installer
+  before publishing
+- VNC (M6) is fully built out: Raw/CopyRect/Hextile/ZRLE/Tight encodings,
+  bidirectional clipboard sync, remote cursor shape sync, and both
+  scale-to-fit and actual-size display modes. Standard VNC Authentication
+  and no-auth servers (TigerVNC, x11vnc, TightVNC, etc.) work end to end.
+  macOS's built-in Screen Sharing uses two undocumented, reverse-engineered
+  authentication schemes that are implemented but not yet confirmed working
+  against a real macOS server — see
+  [docs/PROGRESS.md](docs/PROGRESS.md) for details.
 
 Progress and milestone details:
 - [docs/PROGRESS.md](docs/PROGRESS.md)
 
-Latest release (installers for Windows, Linux, and macOS):
-- [v2026.9.15](https://git.darksingularity.org/DarkSingularity/orbithub/releases/tag/v2026.9.15)
+Latest published release (installers for Windows, Linux, and macOS):
+- [v2026.9.16](https://git.darksingularity.org/DarkSingularity/orbithub/releases/tag/v2026.9.16)
 
 User Guide:
 - [docs/USER_GUIDE.md](docs/USER_GUIDE.md) (also available as a PDF attached to each release, and in-app via `Help -> User Guide`)
@@ -50,6 +57,8 @@ An embedded RDP session in a tab.
 - SQLite-backed profile storage
 - Create, edit, delete profiles
 - Protocol-aware profile validation (SSH/RDP/VNC)
+- Username is optional on any protocol's profile — if left blank, OrbitHub
+  asks for one inline at connect time instead of requiring it up front
 - Profile search and sorting
 - Tags support
 - Folder/subfolder support
@@ -58,13 +67,20 @@ An embedded RDP session in a tab.
   - New Folder
   - New Connection
 - Drag-and-drop profile moves between folders with persistence
+- Import/Export of the whole profile list as JSON, and one-way import from
+  mRemoteNG connection XML files (passwords are never imported)
 
 ### Session Experience
 
 - Multi-tab session window
 - Auto-connect on tab open
 - Disconnect on tab close
-- Session state indicators on tabs
+- Session state indicators on tabs, colored distinctly per state
+  (connecting/connected/disconnected/failed)
+- A tab awaiting a username/password prompt is clearly marked — its title
+  gets a "(Needs input)" suffix and its tab color changes — even when it
+  isn't the tab currently in view, and the inline prompt itself uses a
+  solid highlighted banner rather than blending into the rest of the tab
 - Timestamped event log with filtering and export
 
 ### SSH
@@ -82,14 +98,36 @@ An embedded RDP session in a tab.
 - Domain-aware authentication support
 - RDP security/performance profile options
 
+### VNC
+
+- Embedded in-window VNC rendering surface (no external launcher)
+- Raw, CopyRect, Hextile, ZRLE, and Tight rectangle encodings
+- Bidirectional clipboard sync
+- Remote cursor shape sync
+- Scale-to-fit and actual-size (scrollable) display modes, toggled
+  per-tab and remembered across sessions
+- Standard VNC Authentication and no-auth servers (TigerVNC, x11vnc,
+  TightVNC, etc.)
+- No dynamic remote-desktop resizing (VNC has no real equivalent of RDP's
+  MS-RDPEDISP)
+- macOS Screen Sharing's two undocumented Apple auth schemes are
+  implemented but not yet confirmed working against a real macOS server —
+  see [docs/PROGRESS.md](docs/PROGRESS.md)
+
 ### App UX
 
 - App icon and themed About dialog
+- In-app User Guide (`Help -> User Guide`), matching
+  [docs/USER_GUIDE.md](docs/USER_GUIDE.md)
 - `File` menu:
   - New Profile
   - New Folder
+  - Import Profiles...
+  - Export Profiles...
+  - Import from mRemoteNG...
   - Quit
 - `Help` menu:
+  - User Guide
   - About OrbitHub
 
 ## Build and Run
@@ -140,6 +178,9 @@ Core dependencies:
 - Qt 6 (Widgets, SQL)
 - CMake 3.21+
 - C++17 toolchain
+- OpenSSL (RDP/VNC transport security and Apple VNC auth)
+- zlib (VNC's ZRLE and Tight encodings)
+- libjpeg-turbo (VNC's Tight encoding's JPEG sub-mode)
 
 Protocol/runtime dependencies:
 - SSH client (`ssh`) available on `PATH` for SSH sessions
@@ -176,12 +217,19 @@ See in-app `Help -> About OrbitHub` for license links and third-party inventory.
 
 - `src/` - application source code
 - `docs/` - build guide, spec, and progress tracking
+- `packaging/` - per-platform installer/package build scripts
+- `tests/` - CTest unit/integration tests and fixtures
+- `tools/` - standalone build-time tools (e.g. the User Guide PDF generator)
 - `third_party/` - vendored third-party dependencies
 - `build/` - local build output (generated)
+- `dist/` - packaged installer/deb/flatpak/dmg output (generated)
 
 ## Notes
 
 - Passwords are requested at connect time and are not stored in the profile database.
+- A profile's username is optional for every protocol; if left blank,
+  OrbitHub asks for one inline the first time you connect that profile.
 - VNC support covers standard VNC Authentication and no-auth servers (e.g. TigerVNC, x11vnc,
-  TightVNC); it doesn't yet reach macOS's built-in Screen Sharing server, which uses a different
-  authentication scheme (see docs/PROGRESS.md, Milestone 6).
+  TightVNC). macOS's built-in Screen Sharing server uses two undocumented, reverse-engineered
+  authentication schemes that are implemented but not yet confirmed working against a real
+  macOS server (see docs/PROGRESS.md, Milestone 6).