docs: add strict mode guide and rewrite OPL reference for Keto

[DavudSafarli]

• Adds a new guide what "strict mode" is, why and how to enable it, known breaking patterns with examples, and how to audit your app before enabling.
• New page on how to migrate from using SubjectID to SubjectSets - which is required by strict mode

Summary by CodeRabbit

• Documentation
  • Added a new "Strict Mode" guide entry under the Keto → Guides → Fine-grained Permissions sidebar. This update makes the strict mode documentation discoverable from the Keto guides navigation, helping users locate and access guidance on strict mode behavior and configuration more easily.

[coderabbitai]

📝 Walkthrough

Walkthrough

This PR adds a single documentation navigation entry to the Keto guides section of the sidebar configuration, linking to the new strict-mode guide under the "Fine-grained Permissions" category.

Changes

Documentation sidebar navigation

Layer / File(s)	Summary
Keto strict-mode guide sidebar entry sidebars-network.ts	Added keto/guides/strict-mode as a new doc item in the Keto "Guides" section.

Estimated code review effort

🎯 1 (Trivial) | ⏱️ ~2 minutes

Suggested reviewers

• aeneasr
• piotrmsc

Poem

🐰 I hopped through lines of sidebar code,
A tiny link I gently sowed,
"strict-mode" now stands in tidy row,
For readers seeking rules to know,
Hooray — the docs will gently grow!

🚥 Pre-merge checks | ✅ 4 | ❌ 1

❌ Failed checks (1 warning)

Check name	Status	Explanation	Resolution
Description check	⚠️ Warning	The PR description is minimal and lacks several required template sections including a 'Related Issue or Design Document' section, checklist items, and comprehensive explanation of changes.	Complete the PR description by adding the 'Related Issue or Design Document' section with a reference to issue #2573, fill in the checklist items appropriately, and provide more detailed information about the changes and their motivation.

✅ Passed checks (4 passed)

Check name	Status	Explanation
Title check	✅ Passed	The title accurately reflects the main changes: adding a strict mode guide and rewriting the OPL reference for Keto documentation.
Docstring Coverage	✅ Passed	No functions found in the changed files to evaluate docstring coverage. Skipping docstring coverage check.
Linked Issues check	✅ Passed	Check skipped because no linked issues were found for this pull request.
Out of Scope Changes check	✅ Passed	Check skipped because no linked issues were found for this pull request.

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✨ Finishing Touches

📝 Generate docstrings

• Create stacked PR
• Commit on current branch

🧪 Generate unit tests (beta)

• Create PR with unit tests
• Commit unit tests in branch keto-strict-mode

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[Copilot]

Pull request overview

This PR expands Ory Permissions (Keto) documentation by adding a new guide explaining “strict mode” and by rewriting the Ory Permission Language (OPL) reference from a formal specification into a practical, example-driven how-to.

Changes:

• Added a new “Strict mode” guide covering behavior changes, breaking patterns, and readiness checks.
• Reworked the OPL reference page into a structured guide (namespaces, relations, subject sets, permits) with examples.
• Added the new guide to the network sidebar under Keto guides.

Reviewed changes

Copilot reviewed 3 out of 3 changed files in this pull request and generated 1 comment.

File	Description
sidebars-network.ts	Adds the new strict mode guide to the Keto guides sidebar list.
docs/keto/reference/ory-permission-language.mdx	Rewrites the OPL reference into a practical guide with examples.
docs/keto/guides/strict-mode.mdx	Introduces a new guide explaining strict mode, expected behavior changes, and audits.

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