docs: use nonblocking warnings for paid training workflows

[Omkar More (omkarmore83)]

Summary

Replace separate spending/budget approval prompts with a brief, nonblocking warning for user-requested workflows across managed fine-tuning and interactive training. The policy applies to all users and environments, including Autopilot.

• Mention cost information only when readily available; unknown pricing or a missing dollar budget does not block a requested run.
• Remove the approved argument and permission gate from the documented custom-SFT helper; log a warning before session allocation instead.
• Align setup, evaluation, recipe, recovery, cleanup, and paid-smoke guides with the shared execution contract, and point policy references at this repository.
• Preserve project permissions, required preview access, data/privacy checks, supplied limits, duplicate prevention, resource ownership, and separate deletion confirmation. Unrequested provisioning, deployments, tools, and recurring work remain out of scope; workflow opt-in and environment protections are unchanged.

This is a documentation-only change. Runtime source, dependencies, notebooks, tests, and workflow configuration are unchanged.

Validation

All validation was offline; no paid workflows were run for this change.

• Root navigation/model-eligibility documentation checks: 7 passed.
• Interactive public-documentation contracts: 67 passed.
• Session-local mocked custom-SFT helper checks: 10 passed, covering warning-before-allocation without approval, prepared-data reuse, invalid inputs, checkpoint verification, cancellation/error propagation, and owned-session cleanup.
• Compiled 28 fenced Python examples and checked 297 local/canonical links, including their anchors, across the changed documents.
• git diff --check passed; no private runtime artifacts are included.