fix(agentgateway): remove telemetry source attribution from _lob.py

[tiagoek]

Summary

Requested by @smahr (PR #220) to remove telemetry source attribution from _lob.py specifically, so that internal destination calls made by the LoB auth helpers are not counted as cross-module traffic from AGENTGATEWAY in observability dashboards.

What changes:

• Remove _telemetry_source=Module.AGENTGATEWAY from create_destination_client() in _fetch_auth_token and get_ias_client_id_lob
• Drop the now-unused from sap_cloud_sdk.core.telemetry import Module import
• Bump version to 0.35.1

Why:
Without _telemetry_source, record_metrics treats these calls as user-facing (source=None) rather than internal SDK plumbing. The intent is that the auth/IAS resolution steps in the LoB flow should not show up as AGENTGATEWAY → DESTINATION cross-module metrics — they are transparent infrastructure calls on behalf of the consumer.

Scope intentionally limited to _lob.py:
_fragments.py retains _telemetry_source=Module.AGENTGATEWAY on create_fragment_client() — fragment discovery is a distinct step and that attribution is considered correct. Aligning _fragments.py is out of scope for this PR.

Test plan

• Verify _fetch_auth_token still resolves auth tokens correctly
• Verify get_ias_client_id_lob still returns the client ID correctly
• Confirm telemetry metrics for these paths no longer show source=AGENTGATEWAY

[tiagoek]

SDK Module Review

Check	Status	Findings
bdd	✅ PASS	0
binding-shape	✅ PASS	0
commits	✅ PASS	0
concurrency	✅ PASS	0
constants	✅ PASS	0
deletion-hygiene	✅ PASS	0
deps-supply	✅ PASS	0
disclosure	✅ PASS	0
docs	✅ PASS	0
errors-logging	✅ PASS	0
hardcode	✅ PASS	0
http-hygiene	✅ PASS	0
license-spdx	✅ PASS	0
patterns	✅ PASS	0
pr-size	✅ PASS	0
quality-gate-parity	✅ PASS	0
secrets	✅ PASS	0
telemetry	✅ PASS	0
testing-depth	⚠️ FLAG	1
versioning	✅ PASS	0

Findings (1)

• [FLAG] TD-01 — Bug-fix PR touches src/ but no test files changed (at tests/, no code line to anchor)

1 finding(s): 0 posted as inline comment(s) on the affected lines, 1 not tied to a code line (listed above).

---

Generated by sdk-review-skill · v1

[tiagoek]

Closing in favor of a PR targeting Sebastian's fork directly so he can test on top of his work.