feat: add permission modes and CLI orchestration layer

Permission Modes:
- Add default/plan/auto_accept modes controlling tool access
- Plan mode restricts Task agent to read-only tools only
- Auto-accept mode bypasses approval prompts (with confirmation)

Approval Scaffolding:
- Add ApprovalRule/ApprovalRuleSet for granular tool control
- Pattern-based matching on tool name and arguments
- Default rules for common safe/dangerous patterns
- Prep for future bidirectional approval flow

CLI Refactor:
- Default to Task agent (main orchestrator)
- Add --mode flag and runtime mode switching
- Integrate prompt_toolkit for better UX:
  - Persistent command history (~/.webber_history)
  - Tab completion for commands and file paths
  - Auto-suggest from history
- Deprecate standalone 'explore' command

Other:
- Split CHANGELOG.md into per-package files
- Update AGENTS.md release procedure for both packages

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

AGENTS.md

@@ -192,14 +192,23 @@ Uses prefixed tags:
 **NEVER push a tag before updating version files.** Follow this exact order:
 
 ```bash
-# 1. Update version in pyproject.toml
-# 2. Update CHANGELOG.md with release notes
+# For API releases:
+# 1. Update version in webber-api/pyproject.toml
+# 2. Update webber-api/CHANGELOG.md with release notes
 # 3. Commit the version bump
 git add -A && git commit -m "chore: release api vX.Y.Z"
-
 # 4. Create the tag (AFTER the commit)
 git tag api/vX.Y.Z
+# 5. Push everything together
+git push origin main --tags
 
+# For CLI releases:
+# 1. Update version in webber-cli/pyproject.toml
+# 2. Update webber-cli/CHANGELOG.md with release notes
+# 3. Commit the version bump
+git add -A && git commit -m "chore: release cli vX.Y.Z"
+# 4. Create the tag (AFTER the commit)
+git tag cli/vX.Y.Z
 # 5. Push everything together
 git push origin main --tags
 ```