Align scoped workflow draft port naming with actual semantics

[eanzhao]

Summary

• Pure rename: IWorkflowStoragePort → IWorkflowDraftStore, ChronoStorageWorkflowStoragePort → ChronoStorageWorkflowDraftStore, StoredWorkflowYaml → WorkflowDraft; port methods Upload/List/Get/DeleteWorkflowYamlAsync → Save/List/Get/DeleteDraftAsync; AppScopedWorkflowService.SaveAsync → SaveDraftAsync; matching internal helpers and test stubs.
• Zero behavior change. Motivated by the semantic-drift finding on Refactor/frontend #248 (see Refactor/frontend #248 (comment)): under Refactor/frontend #248/Fix scoped workflow draft handling #249, POST /api/workspace/workflows silently migrated from runtime-commit to draft-only write, but every layer's name still advertised the old semantics, violating CLAUDE.md 命名跟随职责 / API 字段单一语义.
• This is phase 1 of the alignment. Phase 2 (separate PR) will tackle the HTTP path (/api/workspace/workflow-drafts), split WorkflowFileResponse into draft vs committed variants, and decide whether to add an explicit publish endpoint — those all cascade into the frontend.

Why this is phase 1 only

• HTTP path POST /api/workspace/workflows stays. Renaming it would cascade into ~78 frontend files and 3+ frontend test suites.
• WorkflowFileResponse still mixes draft-origin fields (FilePath/DirectoryId) with committed-origin fields (Document/Findings/UpdatedAtUtc). Splitting it is a larger design call.
• IScopeWorkflowCommandPort is not re-wired into Studio saves. If the team decides "save = always draft, publish is a separate user action" then the current shape is correct; if "save = commit" semantics must come back, that's a phase-2 decision.

Test plan

• dotnet build src/Aevatar.Studio.Hosting/Aevatar.Studio.Hosting.csproj — 0 errors
• dotnet test test/Aevatar.Studio.Tests/Aevatar.Studio.Tests.csproj — 203/203 pass
• dotnet test test/Aevatar.Tools.Cli.Tests/Aevatar.Tools.Cli.Tests.csproj — 339/339 pass
• CI
• Manual smoke: Studio editor save still round-trips a workflow through POST /api/workspace/workflows and the frontend sees the saved YAML

🤖 Generated with Claude Code

[codecov]

Codecov Report

❌ Patch coverage is 72.30769% with 18 lines in your changes missing coverage. Please review.
✅ Project coverage is 68.54%. Comparing base (a4a5a92) to head (61a0814).
⚠️ Report is 2 commits behind head on refactor/frontend.

Files with missing lines	Patch %	Lines
...tar.Studio.Application/AppScopedWorkflowService.cs	81.63%	5 Missing and 4 partials ⚠️
...ructure/Storage/ChronoStorageWorkflowDraftStore.cs	12.50%	7 Missing ⚠️
...ication/Studio/Abstractions/IWorkflowDraftStore.cs	80.00%	1 Missing ⚠️
....Studio.Hosting/Controllers/WorkspaceController.cs	0.00%	1 Missing ⚠️

@@                  Coverage Diff                  @@
##           refactor/frontend     #252      +/-   ##
=====================================================
- Coverage              68.55%   68.54%   -0.02%     
=====================================================
  Files                   1109     1109              
  Lines                  77905    77905              
  Branches               10204    10204              
=====================================================
- Hits                   53406    53398       -8     
- Misses                 20595    20601       +6     
- Partials                3904     3906       +2     

Flag	Coverage Δ
ci	68.54% <72.30%> (-0.02%)	⬇️

Flags with carried forward coverage won't be shown. Click here to find out more.

Files with missing lines	Coverage Δ
...osting/StudioHostingServiceCollectionExtensions.cs	100.00% <100.00%> (ø)
...DependencyInjection/ServiceCollectionExtensions.cs	100.00% <100.00%> (ø)
...ication/Studio/Abstractions/IWorkflowDraftStore.cs	80.00% <80.00%> (ø)
....Studio.Hosting/Controllers/WorkspaceController.cs	30.34% <0.00%> (ø)
...ructure/Storage/ChronoStorageWorkflowDraftStore.cs	34.83% <12.50%> (ø)
...tar.Studio.Application/AppScopedWorkflowService.cs	60.64% <81.63%> (ø)

... and 2 files with indirect coverage changes

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