fix: preserve resolved numeric values across declarations

[waywardmonkeys]

Numeric declarations previously lost their payload and options through formatting or repeated evaluation. Retain exact integers and decimals, inherit and override parsed options across annotations, and separate exact/plural selection from display. Use checked offset arithmetic.

Evaluate declarations eagerly, once per formatting execution, including bare :string inputs. This makes errors in unused declarations observable: .local $x = {$missing :number} {{hello}} outputs hello and reports MissingArg. Retain raw string text and direction metadata until output, so a later numeric annotation receives 1 rather than text containing bidi isolates.

Reuse the locals buffer and drop its values before returning on success or error. The catalog verifier rejects uninitialized local access on any reachable path and stores that skip slots, checking each message entry independently. Selector dispatch reads stored values by private slot index without cloning them.

When another selector rejects an exact numeric variant, retry plural/ordinal candidates before wildcard candidates. Validate each source selector once before dispatch, avoiding duplicate BadSelector diagnostics. Emit repeated fallback subtrees once and jump to their continuation while closing intervening select scopes.

Carry failed expressions as Value::Fallback through nested calls and aliases. Skip functions with failed operands without repeating their errors, and preserve each alias's fallback name. Correct declaration diagnostic spans to use document coordinates.

Host::call and Host::call_select gain a recoverable-error callback. New Value variants retain numeric, string, selector, and fallback state; render through Host::format_default to apply direction metadata. Catalogs must be recompiled for the new local/selector instructions. The runtime migration notes cover custom hosts, CatalogError::InvalidLocalSlot, and exhaustive runtime/compiler enum matches.

Current WG result: 415/462 passing, versus the corrected baseline of 404/462. The initial numeric implementation scored 416; the fallback correction exposes one additional mismatch in pattern-selection.json case 12, which expects a cascading bad-operand. The current formatting algorithm short-circuits function resolution for a fallback operand, so that additional error is no longer emitted. The fixture has not been modified.

Recoverable function option resolution is handled in #25. Arena storage and decimal/currency feature expansion remain separate work.

Stacked on #22.

[waywardmonkeys]

Superseded by #26, which contains this change and the reviewed follow-up fixes in the consolidated stack.