Spike: visual artifact parser class (OCR, scanned PDFs) and PPTX

[burakdede]

Parent epic: #8 (post-v0.1 backlog)

Context

§1.4 records that screenshots were promised while OCR was excluded, a real mismatch, and resolved it by removing screenshots and scanned documents from the v0.1 promise and listing them as a future parser class. §5.2 excludes OCR, screenshots, images, audio, video, and PPTX.

Post-v0.1. The v0.1 behavior (refuse clearly) must remain until this ships.

Spec references

§1.4 feedback audit, §5.2 Explicitly out of scope, §8.7 (optional parser adapters), §24.4 parsing quality risk.

Scope

In: an evaluation of the visual/scanned artifact parser class. OCR for scanned PDFs and images, and PPTX, including dependency implications and quality expectations.
Out: shipping a parser in this issue; any change to v0.1's clear refusal behavior.

Design notes

• The blocking constraint is §6.1: no native dependency, no Python sidecar, no compiler toolchain in the core install. Any OCR engine must therefore be an optional package with the same explicit-install contract as the semantic package (§5.6), or be rejected.
• PPTX is a separate, easier question (an OOXML format like DOCX/XLSX) and may be viable much sooner than OCR, the spike should not bundle their fates together.
• Quality expectations must be honest: OCR output is lossy, and §4.4/§24.4 require visible warnings rather than silent degradation.

Acceptance criteria

• Evaluation of OCR options against the §6.1 no-native-dependency constraint, including whether an optional-package model is acceptable.
• Separate assessment and recommendation for PPTX, which needs no OCR.
• Quality and provenance analysis: what locators are achievable for OCR'd content, and how confidence/loss is surfaced as warnings.
• Determinism analysis: whether the chosen engine produces stable output across runs and platforms (a hard requirement for build IDs, §20.3).
• Recommendation with prioritization and follow-up issues, or a recorded decision to defer.
• Until this ships, the v0.1 behavior stands: scanned documents and images are excluded with an explicit out-of-scope warning.

Tests / verification

• Prototype determinism check on a small scanned corpus if an engine is shortlisted.
• Findings recorded as an ADR entry.

Dependencies

Blocked by the v0.1 release (#102).

Definition of Done

The visual-artifact question is answered with evidence, and PPTX is prioritized independently of OCR.