Rebuild the production documentation information architecture

## Parent

- #2

## What to build

Replace the single-page feature list with a navigable production manual covering quickstart, language semantics, modifiers, limits, result and error contracts, Python API, CLI/TUI use, migration, and release support.

## Acceptance criteria

- [ ] The Sphinx toctree exposes task-oriented guides and normative references.
- [ ] Normative pages link to accepted RFC decisions instead of inventing behavior.
- [ ] Every public API and supported syntax form has an executable example.
- [ ] The complete site builds with warnings treated as errors.

## Blocked by

- #2
- #7
- #4
- #5

## RFC-0005 contract

This issue implements RFC-0005's normative/operational/planning documentation split, exact feature-status vocabulary, executable public examples, and strict candidate documentation evidence. Planned syntax must remain visibly planned until its conformance cases become required.

Start with parent issues #2, #7, #4, and #5, then read RFC-0005 and inspect the existing Sphinx toctree and single-page feature list. Organize task-oriented guides and normative references around the stated documentation split, preserving planned status until conformance cases are required. Done means executable examples cover every public API and syntax form, RFC decisions are linked, and the complete site builds with warnings treated as errors.

Written by the indexing model from the issue text.