Remove stale competitive.md references from repo docs

[brianamarie]

Summary

• Remove stale competitive.md references from products/README.md, root README.md, and automation/messaging-impact-map.yml.
• Align contributor-facing docs with reference/content-governance.md: competitive positioning and internal talk tracks stay in private execution systems, not this public repository.
• No product or offering messaging changes.

Why

products/README.md described a competitive.md file per product area, but no such files exist and policy keeps competitive intel private. The impact map still flagged non-existent paths, which added noise to Impact Check suggestions.

Test plan

• Confirm no remaining competitive.md references in tracked files
• Spot-check that products/README.md structure guidance matches content-governance
• CI: prose-and-links, content-governance-checks (no messaging content changed)

Reviewer note

Governance/doc cleanup only. MongoDB ingest PRs (#142, #143, #152) are unchanged; this is safe to merge independently of those.

Made with Cursor

[github-actions]

New File Governance Check

No added markdown files detected.

Doc Coverage Check

No new markdown docs detected.

Duplicate Detector

• Changed markdown docs: 2

No significant overlap detected.

Manual waiver commands (maintainers)

• /governance-ok all or /governance-all
• /governance-ok new-file, /governance-ok doc-coverage, /governance-ok duplicate
• /governance-reset all or /governance-reset with the same token

Waiver JSON is stored in a hidden PR comment (messaging-governance-waiver-data:v1), same pattern as Impact Check.

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_{Triggered by pull_request. Workflow content-governance-checks.yml. Docs: AUTOMATION.md, automation/README.md.}

[github-actions]

Messaging Smart Suggestions

No suggestion candidates were generated for this PR.

---

_{Triggered by pull_request. Workflow smart-suggestions.yml. Docs: AUTOMATION.md, automation/README.md.}

[github-actions]

Messaging Impact Check

• Changed files: 3

No impact rules were triggered.

Manual waiver commands (maintainers):

• /impact-ok all (optional same-line note after all is ignored)
• /impact-all (same as /impact-ok all)
• /impact-ok <exact missing path>
• /impact-reset all
• /impact-reset <exact missing path>

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_{Triggered by pull_request. Workflow impact-check.yml. Docs: AUTOMATION.md, automation/README.md.}