fix(git): materialize draft session for generate

[bashrusakh]

No description provided.

[gemini-code-assist]

Code Review

This pull request refactors session creation and context resolution by introducing a reusable materializeOpenDraftSession helper and transitioning to asynchronous generation session context resolution. Feedback on these changes includes improving type safety and code reuse by leveraging resolveDirectoryKey instead of accessing created.directory directly, simplifying folder assignment logic by reusing the normalized createdDirectory variable, and applying optional chaining to lastChoice.modelID for consistency.

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[gemini-code-assist]

Instead of accessing created.directory directly (which is not type-safe on the Session object and doesn't handle fallback fields like project.worktree), we should leverage the existing resolveDirectoryKey helper. We can define createdDirectory first and reuse it for both persistDraftTarget and subsequent operations to keep the code DRY and robust.

Suggested change

	persistDraftTarget({
	projectId: draftProjectId,
	directory: normalizePath(draftDirectoryOverride ?? created.directory ?? null),
	})
	const draftSyntheticParts = draft.syntheticParts
	const createdDirectory = normalizePath(draftDirectoryOverride ?? created.directory ?? null)
	const createdDirectory = normalizePath(draftDirectoryOverride) ?? resolveDirectoryKey(created)
	persistDraftTarget({
	projectId: draftProjectId,
	directory: createdDirectory,
	})
	const draftSyntheticParts = draft.syntheticParts

[gemini-code-assist]

We can simplify this block by reusing the already resolved and normalized createdDirectory variable instead of duplicating the fallback logic with draftDirectoryOverride || created.directory || null.

  if (draftTargetFolderId && createdDirectory) {
    useSessionFoldersStore.getState().addSessionToFolder(createdDirectory, draftTargetFolderId, created.id)
  }

[gemini-code-assist]

For better type safety and consistency, use optional chaining on lastChoice.modelID as well. This prevents potential static analysis or TypeScript compiler warnings under strict null-checking configurations.

Suggested change

	const lastChoiceModel = lastChoice?.providerID && lastChoice.modelID
	? { providerId: lastChoice.providerID, modelId: lastChoice.modelID }
	: null;
	const lastChoiceModel = lastChoice?.providerID && lastChoice?.modelID
	? { providerId: lastChoice.providerID, modelId: lastChoice.modelID }
	: null;