Bug: spec-kit uses parent git repo instead of .specify directory as root

[mbachorik]

Description

When spec-kit is initialized in a subdirectory that doesn't have its own .git, but a parent directory does, spec-kit incorrectly uses the parent's git repository root instead of the directory containing .specify.

Steps to Reproduce

1. Have a parent directory with git initialized: /work/ (contains .git)
2. Create a subdirectory: /work/my-project/
3. Initialize spec-kit in the subdirectory: cd /work/my-project && specify init
4. Create a new feature: specify new "My feature"

Expected Behavior

• Specs should be created in /work/my-project/specs/
• The .specify directory location should define the project root

Actual Behavior

• Specs are created in /work/specs/ (parent directory)
• git rev-parse --show-toplevel finds the parent's .git and uses that as root

Root Cause

In scripts/bash/common.sh (lines 5-13), get_repo_root() prioritizes git rev-parse --show-toplevel over .specify directory detection:

get_repo_root() {
    if git rev-parse --show-toplevel >/dev/null 2>&1; then
        git rev-parse --show-toplevel    # <-- ALWAYS wins if ANY parent has .git
    else
        # Fallback only used when git completely fails
        ...
    fi
}

The same issue exists in:

• scripts/bash/create-new-feature.sh (lines 171-181)
• scripts/powershell/common.ps1 (lines 4-16)
• scripts/powershell/create-new-feature.ps1

Ironically, there's a correct find_repo_root() function in create-new-feature.sh (lines 77-88) that checks for BOTH .git and .specify, but it's only used as a fallback when git fails completely.

Proposed Fix

Invert the logic - .specify should be the primary marker for spec-kit root:

1. First search upward from CWD for .specify directory
2. If found, use that directory as the spec-kit root
3. Only use git as fallback if no .specify found

This ensures spec-kit respects its own initialization boundary rather than inheriting a parent git repo.