fix(events): prevent silent count:0 from action/entity filter mismatch

[Seraf]

CYCLOID_EVENT_LIST / CYCLOID_PROJECT_EVENTS apply the action/entity filters client-side with exact string matching, so a value that doesn't match the event's real tag (e.g. build where the API emits ci_build) silently returned count:0 — and the Ask-Cycloid companion reported "no events" even when the org was full of activity. The tool descriptions and a test fixture also advertised build, steering callers straight into the dead value.

• Self-correcting empty results: when a filter removes every event but events exist, both tools now return filter_matched_nothing, applied_filters, available_actions, available_entities and a hint, so the caller retries with a valid value instead of concluding "no events".
• Corrected the misleading examples in descriptions/docstrings (drop the non-existent build entity; clarify begin/end are in seconds).
• Fixed the SAMPLE_EVENT fixture (entity build -> ci_build) and extracted _unique_component_canonicals to keep list_project_events under the complexity limit.
• Added regression tests for the filter-miss diagnostic (org + project) plus matching-filter and empty-window no-diagnostic cases.

110 tests pass; pyright strict and flake8 clean.