Update docs for update_wavefields

[icui]

Description

Update naming in docs.

Issue Number

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Checklist

Please make sure to check developer documentation on specfem docs.

• I ran the code through pre-commit to check style
• THE DOCUMENTATION BUILDS WITHOUT WARNINGS/ERRORS
• I have added labels to the PR (see right hand side of the PR page)
• My code passes all the integration tests
• I have added sufficient unittests to test my changes
• I have added/updated documentation for the changes I am proposing
• I have updated CMakeLists to ensure my code builds
• My code builds across all platforms

[Copilot]

Pull request overview

This PR updates documentation to reflect the renaming/removal of the (previously documented) update_wavefields concept, aligning the architecture docs with the current update_medium naming used by the solver implementation.

Changes:

• Removed the specfem::compute::update_wavefields API entry from the compute namespace docs.
• Renamed references in architecture docs from update_wavefields to update_medium.
• Updated the example Kokkos kernel label string from update_wavefields to update_medium.

Reviewed changes

Copilot reviewed 5 out of 5 changed files in this pull request and generated 2 comments.

Show a summary per file

File	Description
docs/sections/api/specfem/compute/index.rst	Removes the stale update_wavefields API entry from the specfem::compute docs index.
architecture/type-system/template-patterns.md	Updates the Kokkos parallel_for example label string to update_medium.
architecture/simulation/workflow.md	Renames workflow steps to update_medium in the canonical forward-simulation sequence.
architecture/core-components/medium-physics.md	Removes update_wavefields from the compute-kernel orchestration table.
architecture.md	Updates architecture-level function table/workflow references to update_medium and removes update_wavefields.

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