feat: add default permission mode + rename accept→edit

- Add "default" permission mode: no flags passed to CC, uses its own
  built-in default (asks about everything). Now the system default.
- Rename "accept" alias to "edit" (acceptEdits) for clarity
- Remove "skip" alias (duplicate of "bypass")
- Update all help text, error messages, tests, and LLM prompts

Co-Authored-By: Claude Sonnet 4.6 (1M context) <noreply@anthropic.com>

tests/features/commands/perm.feature

@@ -7,14 +7,14 @@ Feature: /perm command — change session permission mode
     When user sends "/perm"
     Then reply contains "Usage"
     And reply contains "bypass"
-    And reply contains "accept"
+    And reply contains "edit"
     And reply contains "plan"
 
-  Scenario: Set active session to accept mode
+  Scenario: Set active session to edit mode
     Given user has session "sess01" in "/tmp/proj1"
     And active session is "sess01"
-    When user sends "/perm accept"
-    Then reply contains "accept"
+    When user sends "/perm edit"
+    Then reply contains "edit"
     And reply contains "sess01"
     And session "sess01" has permission mode "acceptEdits"
 
@@ -40,7 +40,7 @@ Feature: /perm command — change session permission mode
 
   Scenario: No active session returns error
     Given no active session for user "user_abc123"
-    When user sends "/perm accept"
+    When user sends "/perm edit"
     Then reply contains "No active session"
 
   Scenario: Set permission on specific conv_id
@@ -53,12 +53,12 @@ Feature: /perm command — change session permission mode
 
   Scenario: Cannot change permission of another user's session
     Given session "sess01" in "/tmp/proj1" belongs to user "other_user"
-    When user sends "/perm accept sess01"
+    When user sends "/perm edit sess01"
     Then reply contains "another user"
 
-  Scenario: New session with --perm accept
-    When user sends "/new myproject --perm accept"
-    Then reply contains "accept"
+  Scenario: New session with --perm edit
+    When user sends "/new myproject --perm edit"
+    Then reply contains "edit"
     And session manager has 1 session for user "user_abc123"
 
   Scenario: New session with --perm plan