fix(sessions): resolve agent version lookup

[Haz3-jolt]

Purpose / Description

Fix new Kiro session attribution so traces and insights use the agent version from the global Observal lockfile instead of falling back to legacy 1.0.0 when the hook cwd is empty or unrelated.

Fixes

No issue linked.

Approach

The session resolver now reads the global lockfile and matches by explicit agent name or id when OBSERVAL_AGENT_NAME is available. Directory remains a disambiguation signal and cwd-only lookup remains available when no agent name exists.

The sessions API now returns agent_version for trace list and detail views. The frontend shows agent version in the traces list and Session Info tab.

How Has This Been Tested?

Ran:

python -m pytest tests/test_resolve_agent_version.py
python -m ruff check observal_cli/sessions/base.py tests/test_resolve_agent_version.py observal-server/api/routes/sessions.py
pnpm --dir web typecheck
OBSERVAL_AGENT_NAME=test python - <<'PY'
from observal_cli.sessions.base import _resolve_agent
print(_resolve_agent('', [], None))
print(_resolve_agent('/tmp/not-lockfile-dir', [], None))
PY

The smoke test resolved test to version 1.1.2 from ~/.observal/lockfile.json for both empty and unrelated cwd values.

Learning (optional, can help others)

The bug was in CLI-side attribution before ingest. The hook had OBSERVAL_AGENT_NAME, but version lookup was cwd-first. Kiro user-scoped installs can store directory as ~/.observal, while hook cwd can be empty or a repo path, so version was sent as null. Insights intentionally treats null version as legacy 1.0.0.

No external links used.

Checklist

• You have a descriptive commit message with a short title (first line, max 50 chars).
• You have commented your code, particularly in hard-to-understand areas
• You have performed a self-review of your own code
• UI changes: include screenshots of all affected screens (in particular showing any new or changed strings)

AI Assistance

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• Yes(Please Specify the tool): Pi coding agent
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[codecov]

Codecov Report

❌ Patch coverage is 50.00000% with 17 lines in your changes missing coverage. Please review.

Files with missing lines	Patch %	Lines
observal-server/api/routes/sessions.py	0.00%	12 Missing ⚠️
observal_cli/sessions/base.py	77.27%	5 Missing ⚠️

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