docs(openspec): add FN-007 Git Connection Model change

- Add proposal, design, specs, and tasks for git connection model
- Include provider adapter, credential storage, SSH key lifecycle specs
- Add repository connection API and git operations specifications

openspec/changes/git-connection-model/specs/git-provider-adapter/spec.md

@@ -0,0 +1,35 @@
+## ADDED Requirements
+
+### Requirement: GitHub adapter implements provider interface
+The system SHALL provide a GitHub adapter that implements the GitProvider interface.
+
+#### Scenario: List repositories
+- **WHEN** the adapter lists repositories for an authenticated user
+- **THEN** it returns a list of repository objects with name, url, and default_branch
+
+#### Scenario: Create deploy key
+- **WHEN** the adapter creates a deploy key for a repository
+- **THEN** it registers the SSH public key with GitHub
+- **AND** returns the key ID
+
+#### Scenario: Validate connection
+- **WHEN** the adapter validates a token
+- **THEN** it verifies the token with GitHub API
+- **AND** returns user information
+
+### Requirement: GitLab adapter implements provider interface
+The system SHALL provide a GitLab adapter that implements the GitProvider interface.
+
+#### Scenario: List repositories
+- **WHEN** the adapter lists repositories for an authenticated user
+- **THEN** it returns a list of repository objects with name, url, and default_branch
+
+#### Scenario: Create deploy key
+- **WHEN** the adapter creates a deploy key for a repository
+- **THEN** it registers the SSH public key with GitLab
+- **AND** returns the key ID
+
+#### Scenario: Validate connection
+- **WHEN** the adapter validates a token
+- **THEN** it verifies the token with GitLab API
+- **AND** returns user information