fix(nemo-insights): export analyst result types from package __init__ and update prompt import path

[mdcox]

Summary

The analyst LLM was crashing with AttributeError: module 'nemo_insights_plugin.analyst.functions.insights' has no attribute 'NewInsight'. The system prompt told the model to call return_result(result=AnalystResult(...)) but gave no import path. The model guessed NewInsight lived in the insights module (the last insights-related module it had used), which was wrong — it lives in analyst.result.

Related Issue

Changes

• Add plugins/nemo-insights/src/nemo_insights_plugin/analyst/__init__.py: exports AnalystResult, NewInsight, and InsightUpdate as the stable public API of the analyst package, decoupling consumers from internal module layout.
• Update the analyst system prompt in agent.py to show the canonical import path (from nemo_insights_plugin.analyst import ...) so the model no longer has to guess.

Type of Change

• Code change (feature, bug fix, or refactor)

Quality Gates

• Tests added or updated for changed behavior
• Existing tests cover changed behavior — justification: 146 non-testbed nemo-insights tests pass; the changed modules are exercised by the existing analyst test suite.
• Tests not applicable — justification:
• Documentation updated for user-visible behavior — the system prompt is the user-facing documentation for the model.
• Documentation not applicable — justification:

Verification

• Pull request title follows the repository's Conventional Commit format
• Every commit includes an appropriate Signed-off-by: trailer (horde@nvidia.com)
• uv run pre-commit run -a passes, or any blocked checks are identified below
• Targeted tests pass, or tests are marked not applicable above
• No secrets, API keys, or credentials are included

Targeted validation:

# Import sanity check
python -c "from nemo_insights_plugin.analyst import AnalystResult, NewInsight, InsightUpdate; print('ok')"
# -> ok

# Non-testbed plugin tests (testbed tests require external services and fail pre-existing)
uv run --frozen pytest plugins/nemo-insights/ --ignore=plugins/nemo-insights/tests/testbed -v
# -> 146 passed, 1 skipped

# Pre-commit (all hooks pass; uv-lock hook reports version mismatch 0.9.30 vs required 0.9.14 — unrelated to this change, uv-lock-check confirms lock is in sync)
uv run pre-commit run -a

[github-actions]

Suite	Lines Covered	Line Rate	Branch Rate
Unit Tests	32002/40616	78.8%	63.6%
Integration Tests	18560/38542	48.2%	20.8%