fix: avoid false crypto weekend warnings on complete intraday windows

[stefan-jansen]

Closes #105

Outcome

CryptoSessionValidator no longer infers a missing weekend from an input having seven rows. Existing chronological gap detection remains unchanged. A complete seven-minute or seven-hour Monday window is valid; deleting actual weekend daily bars still reports the Friday-to-Monday outage. AssetValidator's crypto continuity path receives the same correction. Volume, price, maintenance-window and actual gap rules are unchanged.

This focused repair is independent of the calendar-contract stack and does not claim that the separate canonical calendar-selection migration is complete.

Executed verification

• Base c7b9dfa, regression09c6892: four real SyntheticProvider workflow failures, four controls pass in0.68s. Both direct continuity validation and AssetValidator falsely warn about a missing weekend for seven Monday minute/hour bars. Real missing weekend and complete daily-week controls already pass.
• Current 0bbaa62 includes main 2edaed3 through expected-head-guarded GitHub Update branch. Its two owned files are unchanged from 9735536 and the pre-hold locally qualified 5e7e44d. That earlier revision passed 72 focused tests in 4.31s with two default-marker deselections, ResourceWarning as an error, native thread caps of one, Ruff/format, ty and normal hooks. No local checks or hooks have run on the updated head during the strict hold.
• Current-head hosted coverage run 39057777773 passed 3,928 tests, 292 deselected, with 86.22% coverage against the required 85%. Strict documentation run 39057777791 passed its build, rendered identity checks and artifact upload. Remaining supported native/ecosystem platform gates must finish successfully before merge; these completed results do not replace them.
• Full applicable exact-head CI/resource/package/docs/ecosystem checks run hosted and must finish before ordinary merge. No rerun, skip or check weakening.

AI-assisted implementation and regressions under maintainer direction. Owner reviewed the producing APIs, base/fix results and exact11-line production deletion. No independent reviewer claimed. No release/deployment or modification of published0.2.1.

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