Add minimal smoke validation script and documentation

[binrogithub]

Motivation

• Provide a small, dependency-light smoke check for key CLI flows (preview -> run_id/report.md, MCP tool listing, hc_tools_search and policy/apply behavior).
• Enable quick offline validation with a mock mode so the wiring and output-matching can be validated without external services.
• Make expected-output patterns configurable so the script can be adapted to different CLI output formats.

Description

• Add an executable scripts/smoke_validation.sh that: runs a preview command and parses run_id, verifies the generated report.md, calls mcp list_tools and hc_tools_search, asserts that a demo tenant apply is blocked (expected failure), and asserts that an ops tenant apply succeeds when approvals are supplied; it supports a mock mode (SMOKE_USE_MOCK=1) and configurable commands/patterns via environment variables.
• Add documentation/smoke_validation.md with exact example invocations for mocked and real runs, expected (abridged) outputs, and environment variables to customize matching patterns and command overrides.
• The script uses sed to extract run_id and rg (ripgrep) for pattern assertions, prints clear sectioned logs, and is installed as an executable file in scripts/.

Testing

• No automated tests were executed as part of this change; the script is intended to be run (manually or in CI) using the documented mock example or real CLI commands to validate behavior.

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Codex Task