[CK_BUILDER] Update README.md files to match recent code changes

[shumway]

This is mostly adjustments to enum values so that the docs align correctly with the current code.

Also updated the calendar scope of the project to extend through March 2026.

Note: These README.md files are just internal code documentation for developers, and not part of the public documentation of CK.

[Copilot]

Pull request overview

This PR updates internal README documentation to align with recent code changes in the CK Builder experimental feature. The primary changes involve correcting enum value references and updating project metadata.

Changes:

• Updated ElementwiseOperation enum references from the non-existent NONE to the correct PASS_THROUGH value
• Clarified documentation for signature-level fields (data_type and elementwise_operation)
• Extended project timeline from "October - December 2025" to "October 2025 - March 2026"

Reviewed changes

Copilot reviewed 3 out of 3 changed files in this pull request and generated no comments.

File	Description
experimental/builder/include/ck_tile/builder/testing/README.md	Fixed 4 instances of incorrect ElementwiseOperation::NONE to PASS_THROUGH in code examples
experimental/builder/include/ck_tile/builder/README.md	Updated field descriptions for data_type and elementwise_operation, added documentation for special layout values and bias tensor layouts
experimental/builder/README.md	Extended project development timeline to March 2026 and corrected "CKTile" to "CK Tile"

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[shumway]

I don't understand why there was a copilot review and now other changes are being merged into this PR. It just updates some of our README.md files for the CK Builder, and now it's triggering CI on GPUs (wasting our CI resources for no reason). I just killed the CI, that shouldn't be run on documentation PRs, and there was no to add a commit to this PR.

[shumway]

I just cleaned this PR up again, undoing the merge from develop and resetting to just a README file update. This should not run CI.