perf: correct hosted lifecycle tail

[douglasmonsky]

Summary

• bound Candidate A model-call tail inserts by the runtime SQLite variable limit
• preserve canonical call identities while avoiding per-row JSON encoding in the timed tail
• add Python 3.10 portability coverage and endpoint identity assertions for the 2,000-call tail

Root cause

The hosted ordinary.2000_call_tail path built one 36,000-variable SQLite INSERT. Python 3.10's SQLite binding limit rejected that statement with sqlite3.OperationalError: too many SQL variables, while the prior implementation did not inspect the runtime limit.

Validation

• exact-base Python 3.10 baseline reproduces the too many SQL variables failure; corrected Python 3.10 and 3.14 focused suites pass
• 73-test Candidate A lifecycle/publication/performance/recovery profile passes on Python 3.10 and 3.14
• just v passes
• just vc passes, including distribution build and release verification
• all five frozen budgets and first-sample semantics remain unchanged

This PR is the CK-07R1A corrective prerequisite. It does not modify held PR #394 or shared roadmap authority.