Release prep v1.2.0: qdrant-client floor 1.14.3 (CI-enforced) + live Qdrant v1.15.4 verification

[Udjin79]

Release prep for v1.2.0 — Qdrant compatibility floor + live-server verification

Pre-release check found the declared qdrant-client>=1.10 floor was wrong for the new text-search code. This PR fixes the floor with evidence, enforces it in CI, and aligns the docs with behavior verified against a real Qdrant server.

Dependency floor (empirically established)

• 1.10–1.12: HasVectorCondition not importable — the vector module fails to import.
• 1.13.x–1.14.2: local-mode update_vectors behavior fails the sparse-backfill path.
• 1.14.3 and 1.15.1: full suite green (1422 tests).
• → qdrant-client>=1.14.3,<2, with a new CI test-min-deps job that pins exactly the declared minimum so the floor can never silently drift below reality again.

Live verification against a real server (Qdrant v1.15.4 binary, not local-mode)

All seven scenarios pass: sparse search with server-side IDF ordering, sparse tenant boundary, the MatchText nested should-gate against a real full-text index, gate∘tenant composition, dense-vector preservation in named-layout scrolls, and the has_vector coverage-gap → backfill flow.

One behavioral fact corrected by the live run: real Qdrant servers refuse adding a new sparse space to an existing collection (update_collection → 400). The docs previously implied a config-update path "where the server allows it" — they now state plainly: an existing dense collection migrates to sparse via re-index into a sparse-mode collection; mnemostack sparse-backfill is for the other gap (a sparse-capable collection holding dense-only-written points, e.g. via the async store). The ensure_sparse_space docstring says the same.

Docs

• Compose examples pin qdrant/qdrant:v1.15.4 (the version this release is integration-tested against; previously v1.12.6, which predates the server-side has_vector filter the coverage check needs).
• Server minimums documented: sparse IDF ≥ 1.10, has_vector ≥ 1.13.

Version

1.2.0 in pyproject.toml / __version__; CHANGELOG [Unreleased] closed as [1.2.0] - 2026-07-25. Tagging/publishing happens after merge as usual.