Forecast layers: pick a model run, scrub valid time

[BhattaraiSijan]

Forecast layers: pick a model run, scrub valid time

Builds on the core PR that adds urlReplacements kinds and the layers:configChanged broadcast. Merge that first; this PR's base is its branch.

A forecast has two clocks: when the model ran and what moment it describes. MMGIS has one slider. This collapses the first clock into a choice. A forecast layer's card in the Layer Manager gets a "Model run" dropdown; picking a run pins the layer to it, and the existing timeline scrubs valid time over that run's window. After the pick it is an ordinary time-enabled tile layer: coverage gate, no-data warning, Timeline band and row navigation all work unchanged.

Built against the live NAQFC store served by titiler-multidim. Runs and lead range are read from the service's coordinates endpoints; nothing is hand-listed. No new layer type.

What the plugin does

• A layer with variables.forecast is a forecast layer. On refresh the plugin reads the newest N runs (forecast.runs, default 10) and the lead range from the store, and pins a layer with no run yet to the newest so it never asks for tiles without one. The endpoints are derived from the tile URL: the service before /tiles/ and the first url= store.
• Picking a run writes the run into a {reftime} replacement, an elapsed {lead} replacement counting from it in forecast.leadStep units (default PT1H; P1D, P1M for daily or monthly models), and the run's window into the layer's data times. The clock is moved into the window only if it sits outside it.
• The card shows the runs newest first, named by hour for sub-daily steps and by day or month otherwise, with a lead readout such as +18 h beside the select.
• A block saved with enabled: false is not a forecast, which is what the Configure switch writes when left off. A hand-written block with no enabled key still is.

Authoring

url: ...?url=s3://.../o3_conus&url=s3://.../o3_ak&variable=ozcon&sel=reference_time=nearest::{reftime}&sel=lead=nearest::{lead}&colormap_name=viridis&rescale=0,80
time: { enabled: true, type: "requery", format: "%Y-%m-%dT%H:%M:%SZ" }
variables: { forecast: { enabled: true, runs: 10, leadStep: "PT1H" } }

Documented on the tile layer page. Configure gets a "Forecast runs" row on the tile layer's Time tab (Forecast Layer switch, Lead Step, Runs To Offer, optional Runs URL and Leads URL) and kind, value, from, step fields on the URL tab's replacement editor, so none of this needs hand-edited JSON.

Verified

• Unit coverage for the pure helpers, the apply/select/ensure handlers against a fake bus, the card, and the adapter end to end with a stubbed service. Full suite and TypeScript check pass.
• Live against the NAQFC ozone store: the card lists the newest runs, tiles render, scrubbing changes sel=lead while reference_time stays fixed, picking an older run moves the Timeline band and the tiles, scrubbing past 72 h shows the no-data warning and stops requests.

Follow-ups

• Core's own month stepping overflows Jan 31 + P1M to Mar 3; the plugin clamps, core does not yet.
• Run discovery for STAC-served forecasts, where runs live only in item ids.
• Rescale from /statistics for skewed fields such as PM2.5.

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