The OpenAI-compatible /v1/embeddings fallback path can't pass
`truncate:true` / `num_ctx:8192` to the model, so any chunk that
exceeds the model's loaded context_length (often 2048 for
nomic-embed-text:v1.5) returns a 400 BadRequestError and is silently
dropped from Qdrant. Two CPU-only ingestion runs on NOMAD1 hit this
on dense technical content (medlineplus, arduino.stackexchange) even
after PR #763's num_ctx fix on the native path.
Pre-cap each input string at 4000 chars before either backend call.
That's ~1000-2000 tokens depending on density, comfortably under the
model's 2048 default. The chunker in RagService is sized for
MAX_SAFE_TOKENS=1600 (3200 chars at its conservative 2 chars/token
estimate), so well-formed inputs are never touched; this is purely a
runtime safety net for the edge cases that slip through.
Also stop swallowing the original error in the catch. The bare
`} catch {}` here has masked recurring "input length exceeds context
length" failures for months (#369, #670, #881). Capture and warn-log
the message so future investigations see why we fell back.
Same root cause as #369 and #670 which were closed without an actual
fix to the fallback path.
2dec5bf676