[Luen]

Closes #182. Stacked on #179 → #178 → #177; merge those first (GitHub retargets this to main as they land).

What

• Arrowheads on every move line, in the line's colour with a thin white edge, placed 60% of the way along so they stay clear of the circles at both ends.
• Both directions: when A → B and B → A are both drawn, the two lines shift to either side of their direction of travel. Because the arrows sit at 60%, the two arrows also land at different points. On a shark's page, a there-and-back shark (e.g. 955000004999522: Apaura → Vaiane → Apaura) now shows two parallel lines with opposite arrows.
• /recaptures: one line per direction instead of pooling both. Width = moves that way; the popup reads "A → B · n moves · km".
• Leaflet: an SVG <marker> per line layer, set as marker-mid on each path. Offsets are in screen pixels and recomputed on zoom. smoothFactor: 0 stops Leaflet simplifying away the arrow's vertex. SSR MooreaMap: the same thing with <polyline> and marker-mid.
• Shared geometry in src/lib/components/lineGeometry.ts, with unit tests.
• No new dependencies and no CSP change.

Not covered

• The Play dot still glides along the unshifted centre line (a few px from the shifted line).
• Arrows follow straight lines; once Charts: shortest water routes between nurseries (precomputed GeoJSON) for move lines and animation #183 lands they should follow the water route's final segment.

Checks

pnpm lint, pnpm check, pnpm test, pnpm build, pnpm test:e2e (38 passed). Checked against the real data: the shark page (two directions, zoomed in) and /recaptures (6 directed lines, all with arrows, no console errors).

🤖 Generated with Claude Code

[Luen]

Reviewed all seven changed files, including reversed-pair geometry, direction offsets, SVG marker setup, directed move aggregation and SSR rendering. No additional actionable defect found in this PR's own changes. The unshifted playback dot is an already documented limitation.

Merged the reviewed fixes from #177–#179 into this branch: literal-text point/move tooltips, no playback animation across unknown capture locations, and visible GPS exclusion notices when the adult map has no usable points. Current head: aa03b4b. The branch's arrow implementation is preserved.

Validation: lint, type checks (0 errors/warnings), production build, 126 unit tests and all 41 browser tests passed. Browser regressions cover tooltip HTML injection and the two empty-GPS cases. Two opt-in real-data tests were skipped; private workbook results were not independently reproduced. All updates were fast-forward pushes to the existing branches; PR bases and merge order are unchanged. No merge or deployment performed.

[Luen]

Reviewed #184's directed aggregation, reverse-pair detection, screen-pixel offsets, marker definitions/IDs, midpoint preservation, zoom redraw and SVG fallback. No additional defect found in the arrow implementation itself. The documented playback dot still follows the center line.

Merged the reviewed parent changes from #179 and resolved conflicts in both map components: directed geometry/marker-mid arrows are preserved alongside #178's keyboard access, text-only tooltips and SVG markKeys controls. Added a synthetic browser regression that zooms the map, checks that each move path references an existing arrow marker, and opens move details from the keyboard after redraw. The initial path must contain the interior vertex needed for marker-mid.

Final head d3592f0. Validation: pnpm lint; pnpm check (0 errors/warnings); pnpm test (126 passed, 2 opt-in tests skipped); opt-in real-data import test (1 passed); pnpm build; pnpm test:e2e (44 passed, including the new zoom regression, inherited keyboard/tooltip/GPS regressions, and light/dark axe checks). Merge resolution and test pushed. Review complete; no spreadsheets changed.