chore: sync upstream GSD to v1.38.5 and release v1.38.3

[rokicool]

Summary

• Sync upstream GSD submodule from v1.38.2 to v1.38.5
• Translate 415+ files (6355+ replacements) from Claude Code to OpenCode equivalents
• Add gsd-edit-phase command and workflow for modifying existing roadmap phases in place
• Fix SDK runtime detection defaults from OpenCode to claude
• Add missing objective sections to command files for CI validation
• Add CHANGELOG entry for v1.38.3 and create release tag

Changes

Added

• gsd-edit-phase command for editing any field of an existing roadmap phase
• edit-phase workflow with field-level edits, guarded edits, and depends-on validation
• Post-merge gate to execute-phase workflow
• Supplemental translation config assets/configs/v1.38.5.json

Changed

• Synced 49 files from upstream submodule
• Translated 415+ files to OpenCode equivalents
• Added mode: subagent to 33 agent definition files
• Replaced task() calls with @subagent_type shorthand syntax
• Fixed SDK runtime detection defaults
• Updated 18 workflow files with significant changes

Fixed

• SDK runtime detection defaulting to OpenCode instead of claude
• planCountPattern regex overwriting next line in roadmap progress handler
• Missing objective sections in gsd-graphify.md, gsd-intel.md, gsd-set-profile.md

Verification

• CI pipeline: PASSED
• Forbidden strings check: PASSED
• SDK dist rebuild: SUCCESS