Scan/import wizard: importing a local source dir silently creates no instance, and the auto-registered ~/.dsh home can never be discovered in instance management

[yukitakasama]

Summary

Two closely related defects in the local-environment import wizard (Settings → 导入本机环境, added by issue #31 / PR #34) on Windows, both still present on the latest upstream/main (3a802ae, tag v0.2.4-dev.109):

1. Importing a local source/version directory "always succeeds" but creates nothing — no instance is made and no failure message or reason is ever shown.
2. C:\Users\yuki\.dsh is shown as "已登记 / registered", but it can never be discovered in instance management.

Problem 1: importing a local source dir silently creates no instance

Looking at src-tauri/src/scan.rs (import_scanned, lines 362–456):

• The input.versions loop only pushes a DshVersion record into the config (lines 369–386). Instances are created exclusively from (home, profile) pairs in the homes loop below. So adding a local source checkout / npm tree in the wizard and clicking 导入所选 registers a version, but never creates an instance. The frontend then always shows a success toast 已导入 {instances_added} 个实例 where instances_added is 0 (ImportScanDialog.vue lines 106–114), and the instance list does not change — with zero explanation that a version alone is not an instance.
• Failure paths are silent: if !path.is_dir() { continue; } for versions (line 371) and if !path.is_dir() && home.wsl.is_none() { continue; } for homes (line 390) skip entries without recording any per-item error. ImportReport only has counters (homes_added / versions_added / instances_added / skipped_known), so a completely failed import still reports success.
• New instances always get version_id: cfg.versions.first().map(|v| v.id.clone()).unwrap_or_default() (lines 438–442) — the first configured version, not the one the user picked. If no version exists yet (user only checked profiles), version_id becomes "", and the instance is only discovered to be unlaunchable at launch time via resolve_instance_paths → "版本不存在" (commands.rs line 891). No validation at import time.

Problem 2: auto-registered ~/.dsh can never become a visible instance

• ensure_user_dsh_home (src-tauri/src/config.rs lines 300–319) auto-registers %USERPROFILE%\.dsh as a HOME record (id: "home-user-dsh", name "用户默认 (~/.dsh)") on every config load, but never creates instances for its profiles.
• In ImportScanDialog.vue the checkboxes of home.already_known homes are :disabled="home.already_known" (line 157) and excluded from default selection (if (home.already_known) continue, line 45). Because ~/.dsh is auto-registered, it is always already_known, so its profiles can never be imported as instances through the wizard — nothing to click, no message.
• The instance management page only renders store.instances; since no instance references home-user-dsh, the home never appears there. Net effect: the launcher says the home is "registered", but there is no in-app path from that fact to an importable instance (the only workaround is hand-creating an instance elsewhere).

Repro (Windows)

1. Have an existing C:\Users\yuki\.dsh (auto-registered at launcher startup).
2. Settings → 导入本机环境 → scan: the home appears with the "已登记" tag and all profile checkboxes disabled.
3. Add a local DSH version directory (source checkout or npm tree), click 导入所选 → success toast with 0 instances; the 实例管理 list is unchanged; no error or reason anywhere.

Expected behavior

• Importing a version directory should either create an instance bound to it, or clearly state that a version alone is not an instance; per-item failures/skips should be reported instead of a blanket success toast.
• Already-registered homes should remain importable (don't disable their profiles), or the instances/home pages should surface homes that exist but have no instance.
• version_id for imported instances should reference the version the user actually chose (and be validated), not cfg.versions.first().

Environment

• dsh-launcher upstream/main 3a802ae (v0.2.4-dev.109)
• Windows 11, DSH_HOME C:\Users\yuki\.dsh

[Gu-ZT]

已通过 #40 实现并合入（b6c23bb）：扫描导入报告逐项 added/skipped 结果及原因，支持绑定首选版本；mock 同步补齐。关闭本 issue。