Same treatment as 1.x — the 2.x release notes pin code samples to API
shapes that no longer compile under v3 (e.g. property-style `*_df`
accessors, the bytes-on-element-types methods removed in #845). Build
the pages but don't try to execute them.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

## Summary

- Move `name` / `subscripts` / `parameters` / `description` off
`NamedFunction`, `EvaluatedNamedFunction`, `SampledNamedFunction` onto a
new `NamedFunctionMetadataStore` SoA store, kept as a sibling field on
`Instance` / `ParametricInstance` / `Solution` / `SampleSet`. Same
snapshot-model PyO3 wrappers and `WithMetadata`-based pandas rendering
as PR #843 (which did this for `Constraint` / `DecisionVariable`).
- Parse boundary moves to per-collection:
`Vec<v1::NamedFunction>::Parse` returns `(BTreeMap,
NamedFunctionMetadataStore)`; per-element helpers
(`named_function_to_v1`, `evaluated_named_function_to_v1`,
`sampled_named_function_to_v1`) reattach metadata at emit.
- `Instance::evaluate` / `evaluate_samples` thread the host store onto
the produced `Solution` / `SampleSet`. `SampleSet::get` carries the
store onto each per-sample `Solution`.
- Element-level `to_bytes` / `from_bytes` removed from `NamedFunction` /
`EvaluatedNamedFunction` / `SampledNamedFunction` — same rationale as
#845: a per-element wire round-trip can no longer carry host-stored
metadata, so the methods became misleading rather than safe.
- METADATA_STORAGE_V3.md flipped \`NamedFunction\` from \"deferred —
separate PR\" to \"landed (this PR)\".

## End state

After this PR the v3 SoA metadata story is uniform across all four
metadata-bearing element types (decision variables, regular / indicator
/ one-hot / sos1 constraints, named functions). The only remaining
deferred item in METADATA_STORAGE_V3.md is the two-mode Standalone /
Attached wrapper design for write-through metadata mutation.

## Test plan

- [x] \`cargo test -p ommx --lib\` — 475 passed (incl. new
\`test_instance_roundtrip_preserves_named_function_metadata\` regression
test)
- [x] \`task python:test\` — all adapter + ommx-tests pass; lint +
typecheck clean
- [x] \`cargo insta test --accept\` for the 5
\`instance::logical_memory\` snapshots that gained the new
\`Instance.named_function_metadata;…\` rows
- [x] Format / clippy clean on changed files

---------

Co-authored-by: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

The release-note entry for #845 documents that to_bytes / from_bytes
are removed from the non-top-level types in 3.0.0a3 (Function / Linear
/ Quadratic / Polynomial, Parameter, the NamedFunction family, the
DecisionVariable family), but the migration guide only covered the
Constraint-family removal that shipped in a2 alongside the
Constraint.id rework.

Add a dedicated §12 covering the broader removal, with the affected
type list, rationale, and a Before/After example showing the
container-type round-trip path. Cross-link from §2's existing
Constraint-family aside, renumber the existing §12 (Convenience
additions) to §13, and add a matching item to the migration
checklist.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

## Summary

Polish the v3.0 release notes and the Python SDK migration guide ahead
of cutting the `python-3.0.0a3` tag. No functional / source changes.

### Release notes (`docs/{en,ja}/release_note/ommx-3.0.md`)
- Promote the `## Unreleased` section to `## 3.0.0 Alpha 3` with the
GitHub Release badge matching the a1 / a2 entries.
- Add a one-line note under `## Unreleased` describing how new entries
are appended there as they land and promoted on each release.
- Fix four `v3.0.0a4` / `3.0.0a4` references that should have been
`3.0.0a3` (introduced in #847; EN+JA, lines 142 and 148 each).
- Add a 🆕 entry for the **AttachedX write-through wrappers** (#849,
#850, #852) — `AttachedConstraint` /
`AttachedIndicator/OneHot/Sos1Constraint` / `AttachedDecisionVariable`,
the `.detach()` escape hatch, and the `instance.decision_variables`
shape change to `list[AttachedDecisionVariable]`.
- Move the `removed_reason` column gate entry from the Alpha 2 section
into Alpha 3 (next to the related `*_df` accessor entry), and rephrase
to acknowledge that the initial `include=` gate already shipped in a2
(#796) while a3 finalizes the `kind=` / `include=` / `removed=` dispatch
shape (#847).

### Migration guide (`PYTHON_SDK_MIGRATION_GUIDE.md`)
- Add a new **§12** covering the 3.0.0a3 removal of `to_bytes` /
`from_bytes` from the broader non-top-level types — `Function` /
`Linear` / `Quadratic` / `Polynomial`, `Parameter`, the `NamedFunction`
family, the `DecisionVariable` family (#845). Includes a Before/After
example showing the container-type round-trip path.
- Cross-link from the existing §2 Constraint-family aside so readers
landing in either spot find the full picture, renumber the existing §12
(Convenience additions) to §13, and add a matching item to the migration
checklist.

After this lands, the tagging step in `DEVELOPMENT.md` (`git tag
python-3.0.0a3 && git push origin python-3.0.0a3`) will publish the
release through `release_python.yml`. The `pyproject.toml` files under
`python/ommx`, `python/ommx-tests`, and `python/ommx-*-adapter` are
already at `3.0.0a3` (set in a5d98a7).

## Test plan

- [ ] Visual review of `docs/en/release_note/ommx-3.0.md` and
`docs/ja/release_note/ommx-3.0.md` rendered output (Sphinx)
- [ ] Visual review of `PYTHON_SDK_MIGRATION_GUIDE.md` (GitHub markdown
— read on the PR diff)
- [ ] Confirm `pyproject.toml` versions across `python/ommx*` are
`3.0.0a3` so the tag picks up the right version
- [ ] Sanity-check that the Alpha 3 section's PR list matches what was
merged between `python-3.0.0a2` and the tag commit

🤖 Generated with [Claude Code](https://claude.com/claude-code)

---------

Co-authored-by: Claude Opus 4.7 (1M context) <noreply@anthropic.com>