revert: DEVEX-1653 rt_mode addition — main-path tag-and-release skipped

[pdodgen-revparts]

Reverts #137.

Why

After merge of #137 and Batch 1 Phase 3 PRs (license_api, internal_api, rp_api, catalog_api, vin_decoder_service), all four main-builds that went through the shared build-php-v1 orchestrator FAILED at integration-deploy with empty image_tag → helm YAML crash.

Root cause: Github Tag and Release job was SKIPPED on all runs. Its condition if: \${{ !inputs.rt_mode }} should evaluate true when rt_mode isn't set by the caller, but empirically it's evaluating differently. Calculate Build Tag (same condition) DID run, so this is likely an interaction between the needs: [build] chain (with reusable-workflow matrix) and the untyped rt_mode input.

Reverting to unblock the 4 red main-builds (integration environment redeploys will run once next push lands on each app's main). Fix-forward under a fresh PR: add type: boolean, default: false to rt_mode, and verify tag-and-release fires on a canary before re-merging.

Refs DEVEX-1653.

[cursor]

PR Summary

Medium Risk
Restores a known-good release path but drops release-train tagging until a fix-forward PR reintroduces rt_mode with a typed boolean default.

Overview
Reverts the DEVEX-1653 rt_mode fork in the reusable build-php-v1 workflow so main-line PHP builds again run Calculate Build Tag → matrix build → Github Tag and Release without conditional skips.

Removes the rt_mode input, the compute-rt-tag job (encodium/actions _compute-rt-tag), and the always() / dual-output wiring that chose between dry-run mathieudutour and RT tags. build now only needs: [calculate-tag] and tags images from that job; workflow tag output comes solely from tag-and-release again.

This unblocks failures where tag-and-release was skipped, leaving an empty image_tag and breaking integration deploy / Helm.

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