fix(carve-out): archive session detritus

[hyperpolymath]

Closes #496

This completes the bounded session-artifact cleanup without discarding historical material.

What changed:

• restores four previously deleted root artifacts as byte-preserved archives under docs/archive
• archives two additional stale session deliverables from the AXEL and gatekeeper trees as exact renames
• moves three unregistered reorganisation leftovers into the archive
• promotes four normative language-testing guides into the registered toolchain-readiness-grades/testing home
• removes the dead contractile Just import and repairs stale QUICKSTART/TEST-NEEDS references
• adds a focused regression suite and regenerates the machine-readable registry
• scopes whitespace exceptions to the four exact recovered archive files

Recovered-file SHA-256 values were checked against their last historical Git blobs. No licence or SPDX text was edited.

Verification:

• session-detritus regression suite: 29/29
• Wave 5 language-guide suite: 7/7
• registry generation followed by second --check: clean
• just validate: passed (existing informational RSR Bronze findings remain)
• git diff --check: clean

[mass-delete-ok] The apparent removals are intentional, content-preserving archive moves or promotions into canonical registered locations.

[sonarqubecloud]

Quality Gate passed

Issues
25 New issues
0 Accepted issues

Measures
0 Security Hotspots
0.0% Coverage on New Code
0.0% Duplication on New Code

See analysis details on SonarQube Cloud

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[hyperpolymath]

CI triage after completion:

• All diff-relevant checks pass, including Registry + topology, Repo self-tests, documentation format, CodeQL, SonarCloud, workflow security, licence consistency, debt/exemption ratchets, secret scanning, and language/package policy.
• Allowlist Preflight checked exactly 32 workflow uses and found 0 outside the allowlist, then failed while reading live repository Actions permissions: HTTP 401 Bad credentials. This is the existing HYPATIA_SCAN_PAT/credential boundary, not a content failure.
• Both Hypatia jobs report the established backlog: 120 total medium-or-higher findings, with 82 unfiltered. The unfiltered set is the same 74 HYP-S009 implementation-in-canon findings plus 8 previously observed non-HYP-S009 findings.
• Positive identity check: the sorted 74-path HYP-S009 set hashes to SHA-256 4146215e89683c762eb320aac69417901ca343ceeb6abadc6103c078b853f954, exactly matching the independently recorded main-branch inventory in [umbrella] Estate audit & optimization — make the enforcement real (Waves 0–6) #460.

No baseline or suppression changes are included in this PR.