Port seeded Age completion and Accelerated pages to 26.3 beta

ports/mc263/README.md

@@ -9,7 +9,7 @@ independent Age weather and lighting, multiple authored or seeded celestial
 bodies and eclipses, biome/material completion, and random features/structures.
 Instability, crystal portals, discovery/stations, writing recovery and optional
 integration parity remain unfinished. The latest published beta is
-[1.0.1.93-beta.1](RELEASE_NOTES_1.0.1.93-beta.1.md).
+[1.0.1.98-beta.1](RELEASE_NOTES_1.0.1.98-beta.1.md).
 Use a test world and keep a backup; do not
 substitute this JAR for the 1.21.1 mod or import 1.21.1 saves.
 
@@ -1291,6 +1291,128 @@ and `age material_probe <name> [chunk_x chunk_z]`. The latter examines one
 terrain-stage chunk (default 0,0) without feature, lighting or entity generation. Nothing is committed
 or published without explicit request.
 
+The local `1.0.1.94-beta.1` slice ports **structure-aware completion of explicit
+biome distributions** from 1.21.1. Single Biome without a supplied biome now
+prefers a biome compatible with every authored structure page, when a common
+candidate exists. Cave + Single + Nether Fortresses therefore selects an
+eligible Cave/Nether biome rather than an unrelated cave biome. If there is
+no common candidate, ordinary seeded filling and authored structure overrides
+remain available, as in root.
+
+For multi-biome controllers, each uncovered structure requirement can add one
+compatible biome from the terrain's available pool. This is an intentional
+exception to ordinary minimum-only filling: an already-full pool may gain
+another biome for its structure pages. Supplied biomes, their order and
+duplicate weights remain intact. A supplied Single Biome is never replaced,
+Native remains unchanged, and Dungeons impose no biome requirement. The
+no-controller fallback remains unchanged in this slice.
+
+Test Single Biome + Villages without biome pages, Cave + Single Biome + Nether
+Fortresses, and a multi-biome book with structures. Compare an explicit End
+Single Biome + Villages to confirm that authored override still works.
+`age create_completed_biomes <name> <seed> <terrain> <distribution> [structure-page-id]`
+now accepts an optional structure fixture. Existing Ages are not rerolled;
+restart/reseed retains completed pools. Nothing is committed or published
+without explicit request.
+
+The local `1.0.1.95-beta.1` slice seed-completes **omitted biome controllers**
+in partly authored books, using 1.21.1's first AgeTraits distribution draw.
+Native, Single and Medium are common; the other supported distributions are
+rarer. Explicit controllers still win. Supplied biomes are never discarded:
+a Native roll with authored biomes falls back by count, as does a Single roll
+with multiple biome pages. Other seeded multi-biome controllers are retained,
+so a lone supplied biome may receive a second biome to meet the minimum.
+
+Void without biome pages still uses The Void; supplied Void biome pages keep
+their existing count-based behavior. An omitted controller that rolls Native
+on Cave terrain uses the same seeded Single fallback already used by random
+Ages, since the port has no native multi-cave source. Explicit Native Cave
+behavior remains unchanged. Structure-aware completion from .94 applies to
+the resulting nonnative controller. Full Link-Panel-only random generation
+retains its existing selector and seeds.
+
+Test new terrain-only books without biome controllers, one/two supplied biome
+pages without a controller, and Cave + Nether Fortresses without a biome
+controller. Compare an explicit Single Biome book and restart/revisit.
+`age create_completed_biomes <name> <seed> <terrain> auto [structure-page-id]`
+provides an omitted-controller fixture. Existing Ages are not rerolled.
+Nothing is committed or published without explicit request.
+
+The local `1.0.1.96-beta.1` slice seed-completes **omitted terrain pages** in
+partly authored books. It starts with the same ranked terrain draw as random
+Ages, following 1.21.1's `selectForWriting` model. If that terrain cannot host
+the supplied features/materials, a deterministic fallback chooses a compatible
+terrain in stable profile order. The port also preflights its current biome
+restrictions, avoiding an automatic Cave choice for supplied surface biomes.
+
+Explicit terrain still wins and incompatible explicit combinations remain
+rejected. Missing-terrain Fortress books can now bind using Cave terrain;
+unpaired fluids use supported surface noise terrain. No extra random features
+are added to partly authored books. The original book page list stays intact;
+the chosen terrain is appended only to internal generation input so material
+and color/controller indices do not shift. Sky/color/celestial compilation
+still reads the original pages. Fully random Link-Panel-only Ages retain their
+existing selector. Already-created Ages do not change terrain.
+
+Test several new books with Sky or a feature but no terrain page, Nether
+Fortresses alone, and an unpaired Water page. Compare an explicit Flat book
+and a Plains biome page without terrain; the latter must not choose Cave.
+`age create_auto_terrain <name> <seed> <page-id>` exercises the production
+selector for one-page fixtures. Restart and revisit to confirm persistence.
+Nothing is committed or published without explicit request.
+
+The local `1.0.1.97-beta.1` slice ports **Native Cave biome distribution** from
+1.21.1. A new Cave + Native book now freezes the full recognized Cave/Nether
+biome pool and distributes it with the existing seeded Tiny-region sampler,
+instead of forcing Lush Caves. An omitted controller or random Cave Age that
+rolls Native now uses that same pool rather than converting to Single.
+Random structures inspect the saved pool, so eligible Nether structures are
+no longer hidden behind an assumed Lush-only source.
+
+Existing Single Cave Ages remain Single. Old empty Native Cave records keep
+their Lush fallback; they are not silently expanded on load. Other Native
+terrains remain unchanged, and explicit Native still rejects biome pages.
+Pools persist across restart/reseed; reseeding can still change future region
+layout. Modded biome surface-rule integration remains separate pending work.
+Back up before updating and do not downgrade worlds containing new Native
+Cave pools to earlier beta builds.
+
+Test a **new** Cave + Native Biomes book without individual biome pages,
+explore multiple regions, then restart/revisit. Compare an explicit Single
+Cave book and an existing old Cave Age. The existing
+`age create_completed_biomes <name> <seed> cave native` fixture also checks
+the native source against Tiny's sampler without generating chunks.
+Nothing is committed or published without explicit request.
+
+### Accelerated random block ticks
+
+The local `1.0.1.98-beta.1` slice ports the **Accelerated** environment page
+from 1.21.1. Repeated pages stack: each adds three extra random positions per
+eligible block section per tick. Only already-loaded chunks within one chunk
+of players are candidates; no extra chunks are loaded. Defaults match 1.21.1:
+at most eight candidate chunks and 16,384 attempted positions per Age tick,
+shared across sections with rotating selection. These limits live in
+`config/rivencraft-local.toml` under `accelerated_age`; setting
+`max_random_tick_attempts_per_tick` to zero disables the extra ticks.
+
+This affects random-ticking blocks such as crops and saplings, not entities,
+machines, scheduled block ticks, or the day/night clock. The authored page
+count persists with the Age across unload/reload, reseeding and restart.
+Existing Ages default to zero; pageless random Ages do not gain Accelerated
+automatically. Instability costs remain part of the pending instability port.
+
+Test two otherwise comparable new Ages, one with a single Accelerated page
+and one with repeated pages. Plant crops/saplings with suitable light and
+space, remain nearby, and compare growth. Revisit after restart. The operator
+command `/rivencraft_port age acceleration <name>` reports the saved count
+and current budgets. Disposable-server fixture
+`age create_accelerated <name> <seed> <pages>` checks authoring and bounded
+attempt arithmetic and creates a Flat Age; it does not prove live growth.
+Build and disposable dedicated-server checks passed for counts 0, 1 and 32,
+overflow/disabled budget arithmetic, unload/reload, reseed and full restart.
+No player was connected for the server checks, so live growth remains an
+in-game acceptance check. The test server was stopped and its world removed.
+
 From the repository root:
 
 ```sh