Release 0.6.0

Changed

• Dependency bump: requires apcore >= 0.17.1 (was >= 0.15.1). Adds Execution Pipeline Strategy, Config Bus enhancements, Pipeline v2 declarative step metadata, minimal strategy preset.
• Schema parser: Required schema properties now correctly enforced at CLI option level (was silently optional).
• Approval gate: Fixed inverted logic in annotation type guard; check_approval() now accepts timeout parameter.

Added

• FE-11: Usability Enhancements — 11 new capabilities:
• --dry-run preflight mode via Executor.validate(). Standalone validate command.
• System management commands: health, usage, enable, disable, reload, config get/config set. Graceful no-op when system modules unavailable.
• Enhanced error output: structured JSON with ai_guidance, suggestion, retryable, user_fixable, details. TTY hides machine-only fields.
• --trace pipeline visualization via call_with_trace().
• CliApprovalHandler class implementing apcore ApprovalHandler protocol, wired to Executor.set_approval_handler(). --approval-timeout, --approval-token flags.
• --stream JSONL output via Executor.stream().
• Enhanced list command: --search, --status, --annotation, --sort, --reverse, --deprecated, --deps.
• --strategy selection: standard, internal, testing, performance, minimal. describe-pipeline command.
• Output format extensions: --format csv|yaml|jsonl, --fields dot-path field selection.
• Multi-level grouping: cli.group_depth config key.
• Custom command extension: create_cli(extra_commands=[...]) with collision detection.
• New error code: CONFIG_ENV_MAP_CONFLICT.
• New config keys: cli.approval_timeout (60), cli.strategy ("standard"), cli.group_depth (1).
• New environment variables: APCORE_CLI_APPROVAL_TIMEOUT, APCORE_CLI_STRATEGY, APCORE_CLI_GROUP_DEPTH.
• New files: system_cmd.py, strategy.py.

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