storkit: create 387_story_configurable_base_branch_name_in_project_toml

.storkit/work/1_backlog/387_story_configurable_base_branch_name_in_project_toml.md

@@ -0,0 +1,22 @@
+---
+name: "Configurable base branch name in project.toml"
+---
+
+# Story 387: Configurable base branch name in project.toml
+
+## User Story
+
+As a project owner, I want to configure the main branch name in project.toml (e.g. "main", "master", "develop"), so that the system doesn't hardcode "master" and works with any branching convention.
+
+## Acceptance Criteria
+
+- [ ] New optional `base_branch` setting in project.toml (e.g. base_branch = "main")
+- [ ] When set, all worktree creation, merge operations, and agent prompts use the configured branch name
+- [ ] When not set, falls back to the existing auto-detection logic (detect_base_branch) which reads the current git branch
+- [ ] The hardcoded "master" fallback in detect_base_branch is replaced by the project.toml setting when available
+- [ ] Agent prompt template {{base_branch}} resolves to the configured value
+- [ ] Existing projects without the setting continue to work unchanged (backwards compatible)
+
+## Out of Scope
+
+- TBD