feat: add deployment promote and rollback commands

[Ruari-Phipps]

Summary

Adds poly deployments promote and poly deployments rollback subcommands, allowing users to promote a deployment to a target environment (pre-release or live) and rollback sandbox to a previous deployment version.

Motivation

Enables deployment lifecycle management directly from the CLI, removing the need to use the Agent Studio UI for promotions and rollbacks.

Changes

• Add poly deployments promote --from <id> --to <env> command with optional --message and --force flags
• Add poly deployments rollback --to <id> command with optional --message and --force flags
• Add promote_deployment and rollback_deployment methods to AgentStudioProject, AgentStudioInterface, and PlatformAPIHandler
• Refactor API URL constants: move /adk/v1 prefix from base URLs into individual route constants
• Add new PROMOTE_URL and ROLLBACK_URL endpoint constants
• Remove headers from debug log output

Test strategy

• Added/updated unit tests
• Manual CLI testing (poly <command>)
• Tested against a live Agent Studio project
• N/A (docs, config, or trivial change)

Checklist

• ruff check . and ruff format --check . pass
• pytest passes
• No breaking changes to the poly CLI interface (or migration path documented)
• Commit messages follow conventional commits

Screenshots / Logs

[Copilot]

Pull request overview

Adds deployment lifecycle management to ADK by introducing CLI subcommands to promote deployments across environments and rollback sandbox to a previous deployment, wiring these through the project/interface/platform API layers.

Changes:

• Add poly deployments promote and poly deployments rollback CLI subcommands (with --message, --force, --debug).
• Add promote/rollback methods to AgentStudioProject, AgentStudioInterface, and PlatformAPIHandler.
• Refactor Platform API URL construction to move /adk/v1 from base URLs into route constants and add promote/rollback endpoints.

Reviewed changes

Copilot reviewed 5 out of 5 changed files in this pull request and generated 15 comments.

File	Description
src/poly/project.py	Adds promote_deployment / rollback_deployment methods on the project wrapper.
src/poly/handlers/platform_api.py	Refactors URL prefix handling; adds promote/rollback endpoints and request methods; removes headers from debug logs.
src/poly/handlers/interface.py	Exposes promote/rollback through the higher-level interface.
src/poly/cli.py	Adds new deployments promote / deployments rollback CLI commands and execution paths.

[github-actions]

Coverage Report

Base (main)	PR	Change
72.3%	72.5%	+0.1% ✅

Changed file coverage

File	Coverage	Change
poly/handlers/platform_api.py	35.0%	+1.4% ✅
poly/handlers/interface.py	55.1%	+0.8% ✅
poly/cli.py	55.5%	+2.8% ✅
poly/project.py	69.0%	-0.3% ⚠️
poly/output/json_output.py	87.5%	+25.0% ✅