feat(claude-do): „Claude Help Me"-Button: Claude-Session zur Setup-Fehlersuch

Der Button, der aus „Problem erkannt" ein „Problem gelöst" macht: startet eine interaktive Claude-Session, die dem Nutzer beim Einrichten hilft.

## Warum externes Terminal
Der ConPTY-Stack (`PtyTerminalSession`, `ConPtyPaneView`) liegt in `ClaudeDo.Ui` und ist Avalonia — der Installer ist WPF und referenziert nur Data/Releases/Localization. Beim Fresh Install sind `app\`/`worker\` außerdem noch n

ClaudeDo-Task: 4e196058-38a3-404f-9862-4cb0e90195da

src/ClaudeDo.Installer/CLAUDE.md

@@ -128,16 +128,11 @@ The Apps & Features uninstall string and "Rerun Installer" both point at `<Insta
 
 ## Environment Checks
 
-> **Merge status (2026-08-05): not yet on `main`.** The `Checks/` folder, `SystemCheckPage`,
-> and `ExecutableResolver` described below exist only on unmerged task branches
-> (`claudedo/06aca9b3afec4b939f59b627bfe21737` for the Installer side,
-> `claudedo/40272c0bb3b14562b59c022d09c382b6` for the `ClaudeDo.Worker` wiring). Build/test
-> verification for this section was done against a local scratch integration of both, not
-> against this repo's actual `main`. Merge them (or re-derive equivalent commits) before trusting
-> this section against the checked-out code. See `docs/open.md` for the outstanding gap this
-> leaves (`Checks/` and `SystemCheckPage` are real, but the "Claude Help Me" button and the
-> Config-mode Diagnose section described as follow-ups were never implemented — both follow-up
-> tasks blocked on this same missing merge and shipped no code).
+> **Merge status (2026-08-06): `Checks/`, `SystemCheckPage`, `ExecutableResolver`, and the
+> "Claude Help Me" button below are on this branch.** The 2026-08-05 note about two unmerged
+> task branches applied to an earlier state; the "Claude Help Me" button follow-up has since
+> landed (see below). The Config-mode Diagnose section in `SettingsWindow` is still **not**
+> implemented — see `docs/open.md`.
 
 `Checks/` holds one `IEnvironmentCheck` per concern, run in parallel by `EnvironmentCheckService.RunAllAsync`:
 
@@ -169,8 +164,18 @@ on page entry (`LoadAsync`, guarded against double-entry). "Next" is disabled vi
 subscribes to `PropertyChanged` on the current page so a live recheck can flip it back. A "Recheck"
 button re-runs `EnvironmentCheckService.RunAllAsync` (disabled while already running).
 
-**Not implemented (see merge-status note above):** a "Claude Help Me" button that launches an
-external terminal with a live `claude` session for setup troubleshooting, and a Diagnose section
-in `SettingsWindow` (Config mode) that re-runs the same checks against the installed configuration.
-Both were speced as follow-up tasks; both blocked before writing any code because their prerequisite
-(this section) wasn't on `main` yet.
+**"Claude Help Me" button** (`Core/ClaudeHelpLauncher.cs`) — a second footer button next to
+"Recheck", enabled only when `claude-cli` is `Ok` and `claude-auth` is not `Failed` (`Unknown`
+stays enabled — an indeterminate login state shouldn't block the one feature that could help
+diagnose it). `BuildReportAsync` renders all check results (Id/Severity/Status/Message table,
+plus the full `Detail` of any `Failed` check) and system info (OS, `dotnet --list-runtimes`,
+resolved `git`/`claude` messages, planned install dir/ports) into
+`%TEMP%\claudedo-setup-diagnose.md` — English and hardcoded (an AI assistant reads it, not the
+user) and deliberately excludes credentials/tokens/env-var dumps. `LaunchTerminal` then opens
+`wt.exe -d %TEMP% cmd.exe /k <claude> <prompt>` (or `cmd.exe /k <claude> <prompt>` if `wt.exe`
+isn't resolvable) via the injectable `IProcessLauncher`, pointing the initial prompt at that
+report file. Errors from either step surface as `ClaudeHelpError` on the page, never an
+exception.
+
+**Not implemented:** a Diagnose section in `SettingsWindow` (Config mode) that re-runs the same
+checks against the installed configuration — still speced as a follow-up, no code yet.