[BigGold1310]

Description of your changes

Adds a one-pager proposing a shared foundation for schema generation and
dependency resolution. Document only — no code changes.

Schema generation is wired independently into seven commands today, and each
wiring drops something another one remembers. Four filed issues (#215, #428,
#242, #370) plus one unfiled bug — pins silently moving on unrelated builds —
all trace back to the same missing piece: there is no single implementation
to fix once.

The proposal is that piece: a Resolver ("what does this project depend
on?") and an Engine ("turn that into files"), reachable only through one
constructor, writing one versioned, grouped lock. Nothing generates until a
full resolved set exists, and groups are regenerated whole and swapped in
atomically — which is what closes #215 and #428 structurally rather than
per-call-site.

Two constraints shape it: no behavior change for existing users in the PR
that lands it, and no second foundational rewrite — it has to accommodate
run-level generators (#170, #374), resource-level filtering, and a future
crossplane schema command group without being reshaped. A 7-step roadmap
shows each of those as a layer-3 change.

#435 and #430 reach the same diagnosis by conflicting routes; the
Alternatives section explains why this adopts their ideas as a foundation
rather than picking either as a replacement.

I have:

• Read and followed Crossplane's contribution process.
• [ ] Run ./nix.sh flake check to ensure this PR is ready for review.
• [ ] Added or updated unit tests.
• [ ] Linked a PR or a docs tracking issue to document this change.
• [ ] Added backport release-x.y labels to auto-backport this PR.

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