server: finish rule provenance and route display follow-ups #156

Verified review follow-ups from Codex on 86b2b4d, still present at a726199. The manager classified these as nonblocking. Probes used only public fixtures and in-memory synthetic overrides.

• 4114684899, server/rules.py:258-263. A source-only override leaves the public pool value and placeholder flag unchanged but removes pool_clearance from the mixed-policy notice and labels its citation Private rules. Count a threshold as replaced only when its value is explicitly replaced. The serialized check still exposes placeholder=true; do not claim every warning disappears.
• 4114684904, server/solver.py:337-376. A wall shorter than the battery reports the height threshold with the battery width citation. Include height among deciding rule keys and cite height when it decides the result.
• 4114684908, server/siteplan.py:289-291. With a nonzero meter-to-wall offset, the route starts at the measured meter position but the SVG meter circle is drawn at its wall projection. Align the displayed meter with the measured position.
• 4114684910, server/solver.py:1745-1779. A policy that forbids automatic rejection returns manual_review with only all_spots_fail, while its serialized policy omits allow_reject. Explain the policy reason without implying a geometry uncertainty.
• 4114684906, route model contract. The bot proposed subtracting route.height_ft from meter.pos[1], but meter Y is in the scene frame and the packet contains no ground height. That subtraction mixes coordinate references. Route polyline is explicitly plan-only; clarify whether length_ft excludes vertical connections and what added measurement would support total cable length. No normal-use false PASS was demonstrated by changing only scene-frame Y.

These did not reproduce an unsafe placement under the documented coordinate contract. The separately confirmed meter-wall workspace uncertainty defect is blocking and is not deferred here.