docs(saas-api): keep max-value note to client-facing contract only

[27Bslash6]

Follow-up to #14 (merged). The "Maximum value size" note added there included backend storage-implementation detail; this trims it to the client-facing API contract only.

Keeps: max value size (25 MB) → permanent 413; SDKs treat any 413 as "value too large"; the ceiling MAY change; unrelated to the 512 MB serializer bound.

Docs-only.

Summary by CodeRabbit

• Documentation
  • Updated cache API specification to clarify maximum value size limits and error handling. Values exceeding 25 MB are now documented as being rejected with 413 Payload Too Large error responses. All 413 errors should be interpreted as indicating the submitted value is too large.

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ℹ️ Recent review info

⚙️ Run configuration

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Run ID: 536849e7-6664-466a-a686-309b16e49a50

📥 Commits

Reviewing files that changed from the base of the PR and between cb6917c and 14fa495.

📒 Files selected for processing (1)

• spec/saas-api.md

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Walkthrough

The "Maximum value size" note for PUT /v1/cache/{key} in spec/saas-api.md is reworded on a single line: the explanation of internal chunking and the server-side ceiling vs. storage-cell distinction is removed, while the 25 MB limit, 413 Payload Too Large permanent-error behaviour, and treat-any-413-as-value-too-large guidance are retained.

Changes

SaaS API Specification

Layer / File(s)	Summary
Reword maximum value size note spec/saas-api.md	Removes the internal chunking and server-side ceiling vs. storage-cell explanation from the 25 MB note, keeping the 413 permanent-error and treat-any-413-as-value-too-large guidance.

Estimated code review effort

🎯 1 (Trivial) | ⏱️ ~2 minutes

Possibly related PRs

• cachekit-io/protocol#14: Also modifies spec/saas-api.md to document the PUT /v1/cache/{key} 25 MB maximum value size and 413 Payload Too Large as a permanent "value too large" error — directly overlapping content with this PR.

🚥 Pre-merge checks | ✅ 5

✅ Passed checks (5 passed)

Check name	Status	Explanation
Description Check	✅ Passed	Check skipped - CodeRabbit’s high-level summary is enabled.
Title check	✅ Passed	The title accurately reflects the main change: removing backend implementation details from documentation whilst maintaining client-facing API contract specifications.
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 unit tests (beta)

• Create PR with unit tests
• Commit unit tests in branch security/saas-api-drop-internals

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