Typst paper compile: finish optimization pass and verify output

[isPANN]

Context

Profiling make paper showed docs/paper/reductions.typ took ~27 s to compile. Two hot spots:

1. load-example / load-model-example doing O(n²) linear scans over data/examples.json (228 rules + 193 models, 279 call sites).
2. find-edge / get-reductions-to / get-reductions-from / render-complexity re-scanning reduction_graph.json edges and resolving nodes.at(e.source).name on every call.

Done so far

• Pre-indexed example-db into _rules-index / _models-index dicts keyed by "src->tgt" / problem name. Bucketed lookup + small filter on variant (docs/paper/reductions.typ:17-72).
• Pre-indexed graph-data: _graph-edges-resolved (source/target name resolved once), _edges-by-source-name, _edges-by-target-name, _edge-by-pair, _nodes-by-name. Rewrote find-edge, get-reductions-to/from, render-complexity to use them.

Result: 27 s → ~9.7 s (≈2.8×).

Remaining work

1. Verify PDF output is identical. Compare old vs new reductions.pdf — check page count, figure placement, example renderings, completeness warnings. No semantic regressions.
2. Shrink examples.json (currently 19 MB). rule.solutions[].target_config is 91 % of the file; 26 MB of that comes from a single rule (tracked in KSatisfiability → TimetableDesign reduction: gadget blowup 64·L² seems excessive #1036). Once KSatisfiability → TimetableDesign reduction: gadget blowup 64·L² seems excessive #1036 lands, regenerate the fixture and re-measure.
3. Optional fallback if KSatisfiability → TimetableDesign reduction: gadget blowup 64·L² seems excessive #1036 is slow to land: sparse-encode target_config as target_config_ones: [indices] in the export script, update ~12 call sites in reductions.typ. Expected: 19 MB → ~1.5 MB, compile ~3–4 s.
4. Commit the optimization. Currently the changes live only in a dirty working copy on main.

Files touched

• docs/paper/reductions.typ (indexing helpers + rewritten lookup functions)

Definition of done

• make paper compiles in ≤ 5 s on a warm cache.
• reductions.pdf visually matches the pre-optimization version (spot check + page count).
• No new Typst warnings.
• Optimization committed to main with a short commit message explaining the indexing pattern.

Related

• KSatisfiability → TimetableDesign reduction: gadget blowup 64·L² seems excessive #1036 (root-cause fix for the 26 MB single-rule blowup)