release: prepare v1.81.19 network foundation

[davekilleen]

Linked Issue

• Linear issue: none — this is the release-foundation stage of the accepted historic fleet delivery.

What Changed

• Prepares v1.81.19 from exact merged retry implementation 1df533d90c6ef6beff4fff4634e8aec2a57e897e.
• Updates release version metadata, rescue instructions, lifecycle catalogue metadata, evidence profile, and changelog.
• Intentionally keeps the historic bridge pinned to public dist/release/v1.81.16-281202d.
• Establishes the network-hardened public foundation. After publication, a separate v1.81.20 PR will pin immutable v1.81.19 as the foundation and provide the distinct follow-up.
• Does not claim full historic fleet acceptance; that still requires one fresh complete public two-hop fleet.

Test Plan

• Unit/integration tests added or updated: no new production logic in this version-only PR; the bounded retry regression tests merged in PR Retry transient updater network failures #417 and are included in this release candidate.
• Negative/error-path tests added or updated: covered by PR Retry transient updater network failures #417 for non-network failures, retry exhaustion, changed evidence, and deadline exhaustion.
• Commands run locally:
  • Focused lifecycle, bridge, updater, fleet-workflow, protocol, and distribution Python suites
  • DEX_PYTHON=<project-venv> npm run test:scripts
  • npm run test:hooks
  • npm run test:integrations — 225 tests, 224 passed, 1 skipped
  • npm run check:connections-contract
  • PII and founder-content gates
  • Update journey protocol regeneration and byte-for-byte comparison
  • Release bundle build, checksums, 949-path installed manifest, 27-file catalogue coverage, and Tau-removal check
  • Isolated release-branch build proving v1.81.19 metadata while retaining the v1.81.16 foundation pin

Ralph Wiggum Loop

• I implemented the change.
• I self-reviewed for defects and edge cases.
• I requested specialist review for risky areas (testing/infra/security when relevant).
• I addressed review findings and re-ran checks.

Quality Gates

• I added/updated tests or documented why no tests are needed.
• I added a regression test for bug fixes, or this PR is not a bug fix.
• I validated failure modes / edge cases.
• I updated docs or confirmed no docs impact.
• CI checks for lint + tests + coverage are expected to pass.

Risk & Rollback

• Risk level (low/medium/high): medium — merging this version PR is expected to trigger publication, so exact-head authorization is required after CI and the canary are green.
• Rollback plan: before merge, close the PR. After publication, never move or rewrite release tags; correct forward with a new version.

Docs Impact

• Files updated: CHANGELOG.md and docs/UPDATE-RESCUE.md.

[github-actions]

What this pull request touches

• other parts of Dex — No mapped product journey was detected for these paths.

Gates that will judge this change

• Personal-data gate: added lines must not expose real identities or personal vault content.
• Change-aware gates: source changes are checked for tests, path-contract use, documentation drift, and touched-file coverage.
• Tests and coverage: the Python, MCP, migration, hook, and script suites must remain healthy.
• Safety and quality: security, lint, distribution, path consistency, and large-vault checks still apply.

Based on 7 changed files.