Typed Rust explicit installation, shared programs, and recording

[saulshanabrook]

Purpose

Stacked on #74. Add explicit installation and shared-program export/recording to the typed Rust frontend, addressing the Luminal review without changing its execution algorithms.

Uses the published core revision from egglog#1027.

Changes

• EGraph::install accepts sort descriptions, selected declarations, rules, and rulesets; it installs dependencies but never creates rows or runs rules.
• ProgramBuilder assembles the same commands offline, including scopes, with atomic preflight failures and no EGraph.
• Ordinary execution uses the shared core Program; scoped recording retains native outcomes and actual submitted scope commands.
• Export structured JSON, diagnostic Egglog text, or checked representable source through the shared program.
• Update the existing tutorial/RFC/README and add a small cross-language export example.

Normal expressions do not need descriptor objects. Explicit callable installation uses the existing selector mechanism. Imported core records do not automatically reconstruct typed authoring metadata. Direct observations/extractors are not invented as recorded commands.

Validation

Typed runtime suites, 47 example mains, 35 compile-fail cases, 15 doctests, and nine focused program tests passed. Independent review replayed equivalent offline and recorded 14-command programs and confirmed installation produced no tuples. Scoped strict Clippy passed with only the unchanged replace_box lint allowed. The original dirty review worktree remains untouched.