chore: remove price-oracle and IEKit from docs

[DavidMinarsch]

Summary

• Remove the price-oracle demo (docs/demos/price-oracle/) and its nav entry
• Delete the entire docs/products/index.md Toolkits page and all eight kit SVGs (coordinationkit, govkit, iekit, keeperkit, mechkit, messagingkit, mintkit, mlkit, oraclekit, smpkit) — the page was no longer reachable from any nav entry after the commented-out Toolkits block was dropped
• Remove the price-oracle and IEKit submodules from .gitmodules and the working tree
• Bump mech submodule v0.31.1 → v0.31.2 so check-submodules-versions CI passes
• Clean up references in Makefile (release-message targets), CONTRIBUTING.md (repo-structure tree), CLAUDE.md (Toolkits/Products list), .spelling, scripts/spell-check.sh, and docs/llms.txt
• Drop the commented-out Toolkits nav block in mkdocs.yml — it referenced submodules that were never registered in .gitmodules

Follow-up (separate PR in open-autonomy)

The following published pages still reference the removed demos and should be updated to use hello-world instead:

• docs/advanced_reference/developer_tooling/dev_mode.md — the Dev mode tutorial fetches and runs the Price Oracle AI agent
• docs/key_concepts/fsm_app_introduction.md — uses the price oracle demo to explain the FSM "period" concept
• docs/upgrading.md — parenthetical reference to IEKit as a use_tendermint: false example

Test plan

• tox -e docs — strict-mode build passes locally
• check-submodules-versions — satisfied after the mech bump
• Visual review of the rendered docs/demos/ page once previewed

🤖 Generated with Claude Code

[OjusWiZard]

CI can be fixed by running make prepare-release, it ensures that the submodules are updated.

[DhairyaPatel7]

Cleanup scope check — three loose ends (all non-blocking):

1. CLAUDE.md:16 still lists the removed submodules in the Toolkits/Products line:

   - **Toolkits/Products**: `mech`, `mech-client`, `mech-server`, `IEKit`, `price-oracle`
   

   Drop IEKit and price-oracle here so future sessions aren't pointed at directories that no longer exist.

2. scripts/spell-check.sh:17 still excludes the deleted submodule path:

   mdspell ... '!price-oracle/**/*.md'
   

   The exclusion is a no-op now that the submodule is gone; drop it for consistency with the other reference cleanups.

3. PR description is slightly out of date. The second bullet says "Remove the OracleKit and IEKit toolkit logos from docs/products/index.md, plus the orphan SVGs in docs/images/", but commit cbc61bb actually deletes the entire docs/products/index.md page and all eight kit SVGs (coordinationkit, govkit, iekit, keeperkit, mechkit, messagingkit, mintkit, mlkit, oraclekit, smpkit). Worth rewriting that bullet so the diff matches the stated scope.

Otherwise looks clean — no other references to price-oracle, IEKit, or OracleKit outside HISTORY.md (historical changelog, correct to leave), and mkdocs.yml nav no longer points at any deleted page.

[OjusWiZard]

I also see some referrences of IEKit in the mech repo