Cover is_image_media_type_token non-image prefix arm

CHANGELOG.md

@@ -36,8 +36,9 @@ All notable changes to TEPP are documented here. The format follows Keep a Chang
 
 ## [Unreleased]
 
-- Restored protected-main gate integrity after the consolidation merges: hourly-scheduler prompt-contract tests now assert the gap-baseline-derived task contract (Gap ID naming, no invented weights) instead of stale increment-specific tokens, the operator-gap register inventory matches the live 33-PR queue, `evidence_core::image_unit` non-image/empty-subtype refusals and `load_union_branch_totals` valid-record accumulation have exact coverage, and the README crate fence plus duplicate registry entries stay deduped.
-- Branch-coverage diagnostics on the post-consolidation head exposed two uncovered outcomes in `evidence_core::image_unit` (`is_image_media_type_token` non-image prefix and empty-subtype refusals), one uncovered authored line (the strip-prefix refusal), and lost valid-record coverage for `load_union_branch_totals`; exact red-to-green cases now cover the non-image/empty-subtype data URIs and per-coordinate True/False accumulation.
+- `evidence_core::image_unit::is_image_media_type_token` now executes the `strip_prefix("image/")` None arm (`return false`) from a direct unit test. `contains_base64_image_data_uri` searches `data:image/`, so a `data:text/plain;base64,...` body never reaches that helper; the earlier claim that those public URIs covered the authored line and the False branch was incorrect.
+- Restored protected-main gate integrity after the consolidation merges: hourly-scheduler prompt-contract tests now assert the gap-baseline-derived task contract (Gap ID naming, no invented weights) instead of stale increment-specific tokens, the operator-gap register inventory matches the live 33-PR queue, `evidence_core::image_unit` empty-subtype public-URI refusal and `load_union_branch_totals` valid-record accumulation have exact coverage, and the README crate fence plus duplicate registry entries stay deduped.
+- Branch-coverage diagnostics on the post-consolidation head exposed two uncovered outcomes in `evidence_core::image_unit` (`is_image_media_type_token` non-image prefix and empty-subtype refusals), one uncovered authored line (the strip-prefix refusal), and lost valid-record coverage for `load_union_branch_totals`; exact red-to-green cases cover the public non-image/empty-subtype data URIs (those public URIs do not reach the private `strip_prefix` None arm) and per-coordinate True/False accumulation.
 - Repaired post-consolidation merge fallout that left protected `main` red: restored the lost `return True` in the `check_coverage.py` match-guard branch, removed the shadowed duplicate `load_union_branch_totals` and `_is_multiline_match_guard` definitions plus duplicate workspace-crate entries (`episode_membership`, `analysis_engine`) from the contract tuple and Cargo member arrays, split two union-fused four-tuples back into `(variant, message)` pairs in the `event_core` error table, repaired the fused `identity_recovery_rate` body in `episode_membership::window`, deduplicated the checked-arithmetic eligible-count block in `analysis_engine`, fixed four-argument `unit()` test call sites, rebalanced the README crate-list fence around all 54 unique crates, and deduplicated the `location_membership`/`validation_core`/`tepp_api` architecture-table rows. Also documents private `PLAUSIBLE_IMAGE_MEDIA_TYPES` so `cargo doc -D warnings` passes.
 - Branch coverage JSON now unique-folds `files[].branches` True/False counts across instantiations. Nightly totals on #49 head `1e3e2eb` reported `event_time.rs` 505/506 while every unique site had both arms taken (253 sites × 2 instantiations). Summary-only reports without branch arrays still fail closed on totals. The 100% contract is unique production arms, matching the LCOV authored-line gate. Still not a Kalman filter, not a matrix `expm`, not ESEM estimation, not DSEM, and not ctsem estimation.
 - `psychometric_core` maps overflowing `expm1(a Δt)` / `expm1(2 a Δt)` in `recover_discrete_constant_predictor_effect` and `recover_discrete_process_noise` through the log-space rewrite without a redundant `if !argument.is_finite()` after overflow. Local crate llvm-cov on #49 head `559e7b399473ee90ba3234677dd9ef7f05f7fd2e` was 509/510: the same LLVM `exp`/`expm1` finite-argument proof as L768/L5040. Existing rewrite (`a = 800` / `a = 400`) and overflow (`a = 1e308`) tests remain the contract. Still not a Kalman filter, not a matrix `expm`, not ESEM estimation, not DSEM, and not ctsem estimation.

crates/evidence_core/src/image_unit.rs

@@ -172,8 +172,11 @@ fn is_plausible_image_media_type(media_type: &str) -> bool {
 
 #[cfg(test)]
 mod tests {
-    use super::{embedded_image_units, refuse_base64_image_as_lexical_text};
+    use super::{
+        embedded_image_units, is_image_media_type_token, refuse_base64_image_as_lexical_text,
+    };
     use crate::{DocumentRecord, EvidenceError, SourceArtifact};
+    use std::hint::black_box;
 
     #[test]
     fn jpeg_uri_and_incomplete_prefix_are_classified() {
@@ -217,7 +220,8 @@ mod tests {
 
     #[test]
     fn non_image_and_empty_subtype_data_uris_are_not_lexical_images() {
-        // A non-image media type exercises the strip-prefix refusal arm.
+        // A `data:text/plain` body never matches `data:image/`, so the public
+        // lexical gate stays Ok without calling `is_image_media_type_token`.
         assert_eq!(
             refuse_base64_image_as_lexical_text("data:text/plain;base64,AAAA"),
             Ok(())
@@ -229,6 +233,18 @@ mod tests {
         );
     }
 
+    #[test]
+    fn non_image_media_type_token_refuses_non_image_prefix() {
+        // `contains_base64_image_data_uri` searches `data:image/`, so a
+        // `data:text/plain` body never reaches this helper. Call it directly
+        // so the `strip_prefix("image/")` None arm (`return false`) executes.
+        assert!(!is_image_media_type_token(black_box("text/plain")));
+        assert!(!is_image_media_type_token(black_box("application/json")));
+        assert!(!is_image_media_type_token(black_box(
+            "text/plain;charset=utf-8"
+        )));
+    }
+
     #[test]
     fn common_raster_media_types_are_accepted() {
         let text = "a data:image/png;base64,AAAA b data:image/jpeg;base64,BBBB \