What does this PR do?

Restores the lazy-install path for boto3. The 2026-05-12 supply-chain-hardening pass (#24515) relocated boto3 from the [all] extra into LAZY_DEPS["provider.bedrock"], but agent/bedrock_adapter.py::_require_boto3 was not updated alongside the other adapters and still does a bare try: import boto3 / except ImportError: raise. Fresh installs therefore hit the manual-install error on the very first Bedrock call, even with security.allow_lazy_installs left at the default true.

This PR mirrors the pattern already used by agent/anthropic_adapter.py::_get_anthropic_sdk — call tools.lazy_deps.ensure("provider.bedrock", prompt=False) before the import, swallowing ImportError (the tools.lazy_deps module itself unavailable — e.g. minimal packaging) and generic Exception (FeatureUnavailable when the user has opted out of lazy installs or is offline). The existing manual-install ImportError survives as the final fallback when lazy install is unavailable or fails.

Related Issue

Fixes #24967

Type of Change

• 🐛 Bug fix (non-breaking change that fixes an issue)

Changes Made

• agent/bedrock_adapter.py — _require_boto3() now calls tools.lazy_deps.ensure("provider.bedrock", prompt=False) before the import boto3 attempt, matching _get_anthropic_sdk in anthropic_adapter.py.
• tests/agent/test_bedrock_adapter.py — new TestRequireBoto3LazyInstall class:
  • test_require_boto3_calls_ensure_provider_bedrock patches tools.lazy_deps.ensure and asserts it is called with ("provider.bedrock", prompt=False).
  • test_require_boto3_tolerates_ensure_failure confirms the import still succeeds when ensure() itself raises (FeatureUnavailable fallback).
  • Both tests stub boto3 via patch.dict(sys.modules, {"boto3": <fake>}) so they run in the minimal CI environment that fix(install): use --extra all not --all-extras; drop lazy-covered extras from [all] #24515 / test(bedrock,tts): skip baseline tests for optional deps removed from [all] #24601 established (i.e. without the real boto3 installed).

How to Test

1. On a clean venv with no boto3 installed and security.allow_lazy_installs at the default true, configure the Bedrock provider and start a chat.
2. The first user message should trigger tools.lazy_deps.ensure → pip-install boto3==1.42.89 → normal Converse call, not the manual-install ImportError.
3. Focused regression (with and without boto3):

   # with boto3 present
   pytest tests/agent/test_bedrock_adapter.py::TestRequireBoto3LazyInstall -v
   # 2 passed
   
   # without boto3 (matches CI environment)
   uv pip uninstall boto3 botocore
   pytest tests/agent/test_bedrock_adapter.py::TestRequireBoto3LazyInstall -v
   # 2 passed
   

4. Adjacent suites still green:

   pytest tests/agent/test_bedrock_adapter.py tests/tools/test_lazy_deps.py
   # 163 passed
   

Checklist

Code

• I've read the Contributing Guide
• My commit messages follow Conventional Commits (fix(scope):, test(scope):)
• I searched for existing PRs to make sure this isn't a duplicate (test(bedrock,tts): skip baseline tests for optional deps removed from [all] #24601 is an adjacent CI-fix PR but doesn't touch _require_boto3)
• My PR contains only changes related to this fix (no unrelated commits)
• I've run the affected test suites and all tests pass (pytest tests/agent/test_bedrock_adapter.py tests/tools/test_lazy_deps.py → 163 passed, both with and without boto3 installed)
• I've added tests for my changes
• I've tested on my platform: macOS 15 (Darwin 25.2.0)

Documentation & Housekeeping

• I've updated relevant documentation — N/A (no user-facing doc changes)
• I've updated cli-config.yaml.example — N/A (no config keys changed)
• I've updated CONTRIBUTING.md or AGENTS.md — N/A (no architecture change)
• I've considered cross-platform impact — N/A (pure-Python import path, same on Linux/macOS/Windows)
• I've updated tool descriptions/schemas — N/A (no tool behavior change)

Screenshots / Logs

Before this PR, on a fresh install with security.allow_lazy_installs: true (default):

API call failed (attempt 1/3): ImportError
   Provider: bedrock  Model: arn:aws:bedrock:us-west-2:<REDACTED>:application-inference-profile/<REDACTED>
   Endpoint: https://bedrock-runtime.us-east-1.amazonaws.com
   Error: The 'boto3' package is required for the AWS Bedrock provider.
          Install it with: pip install boto3
          Or install Hermes with Bedrock support: pip install -e '.[bedrock]'

The retry loop exhausts without ever attempting a lazy install. Also reproduced earlier in the session from the model-discovery path:

WARNING agent.bedrock_adapter: Failed to create Bedrock client for model discovery:
The 'boto3' package is required for the AWS Bedrock provider. ...

Both paths go through _require_boto3, so the single-point fix in this PR resolves discovery and chat together.