[Feature request] Custom namespacing and branch naming conventions

[ejaramillom]

Could not track other issues related to custom namespacing or naming conventions, close issue if any other related.

Context
Currently, Spec Kit appears to enforce a strict numeric naming convention for feature branches and spec directories (e.g., 001-feature-name). While this works for linear histories, it becomes restrictive for larger projects organized by domain or module.

Problem
Our project requires separating features by specific domains (e.g., "Manager" features vs. "User" features). The current logic restricts us to a flat numeric list (e.g., 001-*), which makes it difficult to group related specifications and leads to potential ID collisions or confusion as the number of specs grows.

Proposed Solution
We request that the /speckit.specify command and associated scripts be updated to support custom, alphanumeric namespacing conventions. Ideally, this would be configurable via a regex pattern or a config file, allowing us to define our own prefixes.

Desired Behavior
We would like to name our branches and folders using domain-specific prefixes.

• Current supported format:
◦ 001-paycheck-generation

• Desired supported formats:
◦ USR-001-profile-update (User domain)
◦ MNG-001-paycheck-generation (Manager domain)
◦ FIN-002-tax-calculation (Finance domain)

Acceptance Criteria

1. The tool recognizes folders and branches starting with alphanumeric prefixes (e.g., MNG-, USR-) as valid spec contexts.
2. Commands like /speckit.specify correctly parse these IDs to locate the corresponding spec.md files.

Impact
This enhancement will significantly improve repository organization for teams using Domain-Driven Design (DDD) or working in monorepos with multiple distinct product lines.