docs: promote the global workflow principles out of the Operations placeholder

[iuryeng]

Summary

Moves the four global-workflow sections out from under the placeholder # 🟡 OPERATIONS PHASE heading in aidlc-rules/aws-aidlc-rules/core-workflow.md, as described in #584. Closes #584.

## Key Principles, ## MANDATORY: Plan-Level Checkbox Enforcement, ## Prompts Logging Requirements, and ## Directory Structure describe rules that apply across all three phases (adaptive execution, checkbox tracking, audit logging, the aidlc-docs/ layout), but they sat nested under the Operations placeholder — implying they were Operations-specific, and giving the placeholder more apparent substance than it has.

Changes

• The four sections move, byte-for-byte unchanged, into the document's global preamble — after ## MANDATORY: Custom Welcome Message and before # Adaptive Software Development Workflow — where the other always-on ## MANDATORY: sections already live (the issue's suggested placement: global rules presented upfront, before any phase-specific content).
• Heading levels and titles are untouched, so existing anchors keep working (grepped the repo: no links target these sections).
• # 🟡 OPERATIONS PHASE now ends cleanly with its own placeholder content.
• Pure move: the diff is 92 insertions / 92 deletions in one file, net zero.

User experience

A reader (or a model loading the rules) now encounters the global principles once, upfront, alongside the other global MANDATORY sections — instead of finding them after the Operations placeholder and incorrectly associating them with a phase that is explicitly "a placeholder for future expansion". Rule content itself is unchanged.

Checklist

If your change doesn't seem to apply, please leave them unchecked.

• I have reviewed the contributing guidelines
• I have performed a self-review of this change
• Changes have been tested
• Changes are documented

Test Plan

• npx markdownlint-cli2 "aidlc-rules/aws-aidlc-rules/core-workflow.md" → 0 issues.
• git diff --stat → 92 insertions / 92 deletions, single file — reviewers can verify the moved block is identical by comparing the -/+ hunks.
• Grepped the repository for anchor links to the four headings — none exist outside the file itself.
• Honest scope note: no full workflow run on a platform was performed for this PR — no rule text changes, only document position. The sections now load earlier in the file, which if anything increases their prominence for models that weight early context.

Acknowledgment

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