fix(inspector): read min/max from the zone-map table; unify zone ranges (#416)

[dfa1]

Closes #416.

Problem

• vortex inspect (text and --html) showed no min/max for Rust-written files. The inspector read only array-level ArrayStats from flat segments; the Rust writer puts bounds only in the vortex.zoned zone-map table.
• Found along the way: the HTML per-chunk rows for global-dictionary columns showed the dictionary-code range (0/1, 2/3) instead of the values. Confirmed with a test against the old code.

Fix

Reader: one zone-range model

• New Zone(firstRow, rowCount, stats) record + ScanIterator#columnZones(String): the zone-map table with each zone placed on its column rows. Empty when there's no usable zone map (no per-chunk fallback, unlike columnZoneStats).
• Pruning now uses the same ranges. The three per-shape lookups (zoneIndexByOrdinal / zoneIndexByLength / zoneIndexByDictCodeChunk + ZoneWindow + columnChunkCounts + ChunkSpec.chunkOrdinals) collapse into zoneStarts() plus one binary-search range lookup. A window is checked against the zone that contains it, not against its whole covering chunk. That's still conservative (never a partial overlap), and can prune slightly more on merged grids.
• ZonedStatsSchema#tableDtype(Layout, DType): the vortex.zoned/vortex.stats schema dispatch, previously copied in ScanIterator and the TUI.

Inspector

• Column node: fold of all zones, which is exact whatever the chunk alignment.
• Each chunk: fold of the zones that exactly tile its rows. It keeps array-level stats when zone boundaries cut through it.
• The "walk down to the chunks" logic moves from HtmlReport into InspectorTree#chunkParts, shared with the zone application.

Not deduplicated, on purpose

The TUI's zone-table view keeps decoding the raw table. Switching it to columnZones would lose decimal bounds (ArrayStats boxes decimals to null), single-stat tables, _is_truncated flags, multi-segment tables and nested zoned nodes. Only the schema dispatch is shared.

Tests

• JNI-written file: text + HTML show min/max (failed before).
• Global-dict column: HTML chunk rows show values, not codes (failed before; verified by reverting the inspector).
• columnZones: legacy one-per-chunk ranges, unknown column → empty, Rust stride tiles [0, n) with each zone's min/max matching its own rows.
• Full ./mvnw verify is green.

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