A present zero-byte .jsonl.zstd file was treated as though no artifact existed because readRaw returned undefined when frame scanning found nothing. That contradicted both the plaintext path and the logical zstd reader, and it made the export endpoint answer 404 for on-disk corruption.
Treat a present artifact without a complete header frame as corruption and reuse the zstd reader's existing diagnostic. The regression test now distinguishes an existing empty file from an absent path, and the bilingual JSONL storage contract records that zero-frame artifacts reject alongside other header and frame failures.
SessionPersistence.readRaw previously used undefined for two unrelated states: a supported backend could not find the requested session, or the backend had no per-session artifact concept at all. The export endpoint consequently reported an existing SQLite-backed session as HTTP 404, which falsely diagnosed storage capability as session absence.
Make raw-artifact support an explicit backend capability. Unsupported backends now fail their inherited readRaw path loudly and the host answers 501 before reading, while undefined retains the single meaning of an absent artifact on a supporting backend. First-party backends, test providers, generated API catalogs, bilingual persistence docs, and export error contracts now state that distinction; focused tests cover both the 501 and the inherited rejection.
The export endpoint already streams a ZIP response, but the web client immediately converted that response into a Blob. That forced the complete archive through JavaScript memory before a download could start and coupled transport, buffering, object-URL lifetime, and filename handling to the trajectory view.
Navigate a temporary download anchor directly to the export endpoint instead. The browser now owns streaming and HTTP failure presentation, while a standalone delivery module owns URL construction and filename sanitization. Focused tests cover the handoff, rejection behavior, and the assembled session view; the package README and feature note record the new ownership boundary.
Only `docs/module-graph.*` conflicted; generated, so taken from master and
regenerated. `api-proxy.ts` auto-merged — this branch's history read
(`historySourceFor` / `presenterScopeFor` / `historyCutOf`, in that order)
is intact.
Hook bypassed as before: the staged-pairing check hands an archived note path
to `verify-translation-pairing`. The full-corpus gate passes.
The bubble clamped horizontally and did nothing vertically, so a long
label under an anchor low on the page ran off the bottom. Preset cards
made that the common case: custom presets sit at the end of the roster
and carry the longest descriptions.
A `top` or `bottom` bubble now flips to the other side, and only into a
side that genuinely fits — an anchor with room on neither keeps the
requested placement rather than oscillating. Sliding the bubble
vertically instead would cover the text being read.
