Integrate Iseberg as a native PowerShell ISE profile

[Marc-André Moreau (mamoreau-devolutions)]

Summary

Default desktop builds and release packages remain NativeAOT. Iseberg is disabled by default and requires an explicit -p:EnablePowerShellIse=true managed developer build.

• Import and adapt licensed Iseberg source into DT as a distinct PowerShell ISE (Iseberg) profile, without an external application or cross-repository dependency. Preserve MIT/editor notices under docs/licenses, retain distribution notice output, and record source revision and provenance.
• In the opt-in build, embed the script editor above DT's native terminal, sharing one installed PowerShell runspace per ISE tab. Preserve ordinary PowerShell profiles, isolate tab state, and implement cancelable close, disposal, leased recovery, and explicit error handling.
• Harmonize profile creation and settings with canonical nested ise settings, Defaults, legacy aliases, reversible type conversion, and host-owned Options routing. Default builds preserve saved Iseberg profiles but do not offer new Iseberg profiles or silently launch them as ordinary terminals.
• Add portable original-ISE features, original built-in themes plus Classic ISE/Dark/Light/Follow DT, corrected completion-description rendering, a square profile logo, and compact DT-aligned layout/font proportions.
• Restore Windows, Linux and macOS release workflows and packaging to NativeAOT desktop payloads. The separately validated managed Iseberg publish is not a release payload. The dt CLI remains NativeAOT in both variants; installed PowerShell runtime payloads are not redistributed.

Validation

• Fresh default win-x64 Release publish succeeds without an Iseberg override. Both desktop and CLI are native PE executables without CLR headers; output excludes Iseberg, PowerShell engine and CoreCLR payloads. NativeAOT CLI --help exits zero.
• After default restoration: 291 passed, 0 failed, 0 skipped across default App (213), UI (14) and Settings.Editor (64) suites. Explicit opt-in App/UI reruns: 1,197 passed, 0 failed, 0 skipped (533/664). These are separate build variants, not a combined coverage count.
• Full Iseberg-enabled affected baseline: 1,570 passed, 0 failed, 9 skipped across App, UI, Settings, Settings.Editor and Connection. All nine skips are Unix-only PTY cases on Windows.
• Previously verified managed Iseberg publication, expected rejection of ISE-enabled AOT/trimming, required legal notices, and installed-runtime payload boundary. Relocated legal texts are unchanged and were verified in desktop build output.
• Validated platform script syntax, release workflow YAML and selection of native release artifacts separately from managed validation output. Cross-platform macOS legal-notice regressions pass; the full macOS metadata check requires unavailable plutil on this Windows host.
• Cua Driver verified normal profile creation/settings and actual execution in the opt-in published editor/native console and ordinary PowerShell tab. Test-owned app closed normally through its unsaved-script prompt; user-owned processes/documents were not modified. Square logo checked at 16/24/32 pixels.

Compatibility and scope

The in-process PowerShell engine is not NativeAOT-safe. Enabling it explicitly makes the desktop managed and untrimmed; default releases do not enable it. A future NativeAOT-compatible Iseberg would require an architectural change such as an out-of-process engine.

docs/iseberg.md maps requirements to regression evidence and deployment settings. docs/iseberg-parity.md documents the part-by-part original ISE comparison and portable feature boundaries. Microsoft ISE decompilation remains local, ignored audit evidence and is not included in this PR.

Linux/macOS runtime/package certification and installed Windows package certification remain unverified locally. This does not claim full original WPF/add-on, $psISE API, or Windows PowerShell 5.1 equivalence.