v19: add reading builders and receipt-bearing read results

[flyingrobots]

Part of #712.

Problem

First-use reads currently expose too much optic and coordinate ceremony. v19 should let application code ask a bounded question through reading, while the runtime lowers that question to formal optics internally.

Target Shape

const result = await timeline.read(
  reading.property({
    subject: 'user:alice',
    key: 'role',
  }),
);

result.value;
result.receipt;

Scope

• Add root reading builders for common bounded questions.
• Add ReadingResult with value and receipt.
• Keep Optic as the advanced execution/proof shape.
• Add a provenance-light convenience only if it is clearly named, such as readValue().

Acceptance

• Primary reads return receipts by default.
• Missing basis or operational uncertainty can return obstructed/underdetermined receipts where appropriate.
• Ordinary app docs do not require prepareOpticBasis(), coordinate(), or optic().
• Advanced docs still explain the Reading-to-Optic lowering.

[coderabbitai]

🔗 Related PRs

#642 - Close materialization boundary proof [merged]

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