Remove mounted sandbox runtime compatibility

[chubes4]

Summary

• Remove DMC's mounted-runtime emission of the deprecated sandbox workspace alias.
• Stop accepting the legacy sandbox workspace input alias and remove the MountedSandboxBootstrap class alias.
• Update README guidance so runtime owners translate legacy aliases before handing context to DMC.
• Tighten mounted runtime regression coverage to assert the sandbox-era alias and class alias are absent.

Tests

• php tests/mounted-runtime-context.php
• php -d open_basedir="/Users/chubes/Developer/data-machine-code@cook-remove-sandbox-runtime-compat-20260624:/tmp" tests/mounted-runtime-open-basedir.php
• php -l inc/Runtime/MountedRuntimeBootstrap.php && php -l tests/mounted-runtime-context.php && php -l tests/mounted-runtime-open-basedir.php
• composer install
• for test in tests/*.php; do php "" || exit 1; done

Risks

• Any remaining external caller that still passes sandbox_workspace directly to DMC must now translate that to runtime_workspace before invoking the mounted runtime bootstrap.
• Any external caller that references DataMachineCode\Runtime\MountedSandboxBootstrap directly must move to MountedRuntimeBootstrap.

AI assistance

• AI assistance: Yes
• Tool(s): openai/gpt-5.5 via OpenCode
• Used for: Implementing the compatibility cleanup, updating tests/docs, running verification, and drafting this PR description.

[homeboy-ci]

Homeboy Results — data-machine-code

Lint

✅ lint — passed

ℹ️ Full options: homeboy docs commands/lint
Deep dive: homeboy lint data-machine-code --changed-since e2f3a5d

Artifacts and drill-down

• CI results artifact: homeboy-ci-results-data-machine-code-lint-quality-Linux-node24 contains immediate command JSON for this action invocation.
• Observation artifact: homeboy-observations-data-machine-code-lint-quality-Linux-node24 contains exported Homeboy run history for deeper queries.
• Drill-down: download the observation artifact, then run homeboy runs import <dir>, homeboy runs list, and homeboy runs findings <run-id>.
• Artifacts are attached to the workflow run: https://github.com/Extra-Chill/data-machine-code/actions/runs/28073006285

Test

✅ test — passed

ℹ️ Auto-fix lint issues: homeboy refactor data-machine-code --from lint --write
ℹ️ Collect coverage: homeboy test data-machine-code --coverage
ℹ️ Save test baseline: homeboy test data-machine-code --baseline
ℹ️ Pass args to test runner: homeboy test -- [args]
ℹ️ Full options: homeboy docs commands/test
Deep dive: homeboy test data-machine-code --changed-since e2f3a5d

Artifacts and drill-down

• CI results artifact: homeboy-ci-results-data-machine-code-test-quality-Linux-node24 contains immediate command JSON for this action invocation.
• Observation artifact: homeboy-observations-data-machine-code-test-quality-Linux-node24 contains exported Homeboy run history for deeper queries.
• Drill-down: download the observation artifact, then run homeboy runs import <dir>, homeboy runs list, and homeboy runs findings <run-id>.
• Artifacts are attached to the workflow run: https://github.com/Extra-Chill/data-machine-code/actions/runs/28073006285

Audit

✅ audit — passed

Deep dive: homeboy audit data-machine-code --changed-since e2f3a5d

Artifacts and drill-down

• CI results artifact: homeboy-ci-results-data-machine-code-audit-quality-Linux-node24 contains immediate command JSON for this action invocation.
• Observation artifact: homeboy-observations-data-machine-code-audit-quality-Linux-node24 contains exported Homeboy run history for deeper queries.
• Drill-down: download the observation artifact, then run homeboy runs import <dir>, homeboy runs list, and homeboy runs findings <run-id>.
• Artifacts are attached to the workflow run: https://github.com/Extra-Chill/data-machine-code/actions/runs/28073006285

Tooling versions

• Homeboy CLI: homeboy 0.259.0+b3d82bf59679+7f71199
• Extension: wordpress from https://github.com/Extra-Chill/homeboy-extensions
• Extension revision: 4c646d68
• Action: unknown@unknown