[Bug]: extension add --dev broken

[grissiom]

Bug Description

--dev mode does not install files in symbol link.

Steps to Reproduce

Example command: specify extension add --dev ~/projects/spec-kit-v-model and the file is not link:

~/projects/toyproj% ls -l .github/agents 
total 464K
-rw-rw-r-- 1 grissiom grissiom  11K May  5 12:24 speckit.analyze.agent.md
-rw-rw-r-- 1 grissiom grissiom  20K May  5 12:24 speckit.checklist.agent.md
-rw-rw-r-- 1 grissiom grissiom  14K May  5 12:24 speckit.clarify.agent.md
-rw-rw-r-- 1 grissiom grissiom 8.1K May  5 12:24 speckit.constitution.agent.md
-rw-rw-r-- 1 grissiom grissiom 1.9K May  5 12:24 speckit.git.commit.agent.md
-rw-rw-r-- 1 grissiom grissiom 3.3K May  5 12:24 speckit.git.feature.agent.md
-rw-rw-r-- 1 grissiom grissiom 1.6K May  5 12:24 speckit.git.initialize.agent.md
-rw-rw-r-- 1 grissiom grissiom 1.5K May  5 12:24 speckit.git.remote.agent.md
-rw-rw-r-- 1 grissiom grissiom 1.9K May  5 12:24 speckit.git.validate.agent.md
-rw-rw-r-- 1 grissiom grissiom  11K May  5 12:24 speckit.implement.agent.md
-rw-rw-r-- 1 grissiom grissiom 6.1K May  5 12:24 speckit.plan.agent.md
-rw-rw-r-- 1 grissiom grissiom  16K May  5 12:24 speckit.specify.agent.md
-rw-rw-r-- 1 grissiom grissiom 9.3K May  5 12:24 speckit.tasks.agent.md
-rw-rw-r-- 1 grissiom grissiom 3.8K May  5 12:24 speckit.taskstoissues.agent.md
-rw-rw-r-- 1 grissiom grissiom  19K May  5 12:24 speckit.v-model.acceptance.agent.md
-rw-rw-r-- 1 grissiom grissiom  19K May  5 12:24 speckit.v-model.architecture-design.agent.md
-rw-rw-r-- 1 grissiom grissiom 8.2K May  5 12:24 speckit.v-model.audit-report.agent.md
-rw-rw-r-- 1 grissiom grissiom  18K May  5 12:24 speckit.v-model.hazard-analysis.agent.md
-rw-rw-r-- 1 grissiom grissiom 6.9K May  5 12:24 speckit.v-model.impact-analysis.agent.md
-rw-rw-r-- 1 grissiom grissiom  25K May  5 12:24 speckit.v-model.implement.agent.md
-rw-rw-r-- 1 grissiom grissiom  18K May  5 12:24 speckit.v-model.integration-test.agent.md
-rw-rw-r-- 1 grissiom grissiom  18K May  5 12:24 speckit.v-model.module-design.agent.md
-rw-rw-r-- 1 grissiom grissiom  18K May  5 12:24 speckit.v-model.peer-review.agent.md
-rw-rw-r-- 1 grissiom grissiom  15K May  5 12:24 speckit.v-model.plan.agent.md
-rw-rw-r-- 1 grissiom grissiom  17K May  5 12:24 speckit.v-model.requirements.agent.md
-rw-rw-r-- 1 grissiom grissiom  16K May  5 12:24 speckit.v-model.software-architecture-design.agent.md
-rw-rw-r-- 1 grissiom grissiom  17K May  5 12:24 speckit.v-model.system-design.agent.md
-rw-rw-r-- 1 grissiom grissiom  15K May  5 12:24 speckit.v-model.system-test.agent.md
-rw-rw-r-- 1 grissiom grissiom  18K May  5 12:24 speckit.v-model.tasks.agent.md
-rw-rw-r-- 1 grissiom grissiom  12K May  5 12:24 speckit.v-model.test-results.agent.md
-rw-rw-r-- 1 grissiom grissiom  21K May  5 12:24 speckit.v-model.trace.agent.md
-rw-rw-r-- 1 grissiom grissiom  19K May  5 12:24 speckit.v-model.unit-test.agent.md

Expected Behavior

the extension agents should be link

Actual Behavior

the agent files are copied.

Specify CLI Version

0.8.5

AI Agent

GitHub Copilot

Operating System

Linux

Python Version

3.12.3

Error Logs

Additional Context

No response