fix: Updated the startup and shutdown events, now they are using life…

[DebanKsahu]

Summary

I changed the startup and shutdown events from python sdk. Previously it was using deprecated on_event() method but I replaced it with lifespan which handle both shutdown and startup event.

Type of change

• Bug fix
• New feature
• Refactor / cleanup
• Docs only
• Tests only
• CI / tooling
• Breaking change

Test plan

• ./scripts/test-all.sh
• ./scripts/coverage-summary.sh was run locally, but it currently stops at sdk-python because the local .venv is missing pip.
• Verified the branch rebases cleanly on latest upstream/main.

Before asking for review, please confirm:

• I ran tests for the surface(s) I changed locally.
• New code paths are covered by tests in this PR (no bare additions).
• If I removed code, I updated coverage-baseline.json in
  this PR only if the removal caused a legitimate regression and I
  called it out in the summary above.
• The coverage gate check is green in CI before requesting review.

Checklist

• I have read CONTRIBUTING.md (if present) and
  docs/DEVELOPMENT.md.
• Commits are signed and follow conventional-commits style.
• I have linked any related issues (Fixes feat(tests): add unit tests for vector memory handler functionality #123 / Closes test: add tests for TypeScript SDK utils (pattern, schema, httpAgents) #456).

Related issues / PRs

Fixes #628

[CLAassistant]

All committers have signed the CLA.

[santoshkumarradha]

Thanks for taking this on. Moving off the deprecated startup/shutdown hooks is the right direction. I left one blocker inline because this version replaces the app lifespan outright, which can break callers that already pass their own FastAPI lifespan into Agent.

[github-actions]

Performance

SDK	Memory	Δ	Latency	Δ	Tests	Status
Python	9.4 KB	+4%	0.31 µs	-11%	✓	✓

✓ No regressions detected

[github-actions]

📊 Coverage gate

Thresholds from .coverage-gate.toml: per-surface ≥ 84%, aggregate ≥ 85%, max per-surface regression ≤ 1.0 pp, max aggregate regression ≤ 0.50 pp.

Surface	Current	Baseline	Δ
control-plane	87.10%	87.40%	↓ -0.30 pp	🟡
sdk-go	92.10%	92.00%	↑ +0.10 pp	🟢
sdk-python	93.73%	93.73%	↑ +0.00 pp	🟢
sdk-typescript	90.50%	90.42%	↑ +0.08 pp	🟢
web-ui	84.83%	84.79%	↑ +0.04 pp	🟡
aggregate	85.67%	85.75%	↓ -0.08 pp	🟡

✅ Gate passed

No surface regressed past the allowed threshold and the aggregate stayed above the floor.

[github-actions]

📐 Patch coverage gate

Threshold: 80% on lines this PR touches vs origin/main (from .coverage-gate.toml:thresholds.min_patch).

Surface	Touched lines	Patch coverage	Status
control-plane	0	—	➖ no changes
sdk-go	0	—	➖ no changes
sdk-python	0	—	➖ no changes
sdk-typescript	0	—	➖ no changes
web-ui	0	—	➖ no changes

✅ Patch gate passed

Every surface whose lines were touched by this PR has patch coverage at or above the threshold.