docs: preserve the August engineering trajectory checkpoint

[Chris0Jeky]

Purpose

Preserve the useful parts of the external 2026-08-21 Taskdeck audit as a dated trajectory checkpoint, without presenting its issue states, release conclusions, counts, or maturity judgments as current repository truth.

The repository has advanced substantially since the original analysis. This PR therefore reconciles the checkpoint against current main (2cdc4525766101211fe04787e23bfb46b6aa4011) and current source rather than copying the original report wholesale.

What survives

• the measured August baseline for code, tests, documentation, tooling, workflows, ADRs and GitHub delivery
• the architectural finding that Taskdeck's strongest differentiator is its human-authority boundary around machine-proposed work
• the engineering-economics observations around assurance, agentic throughput, backlog semantics, documentation cost and replacement effort
• durable cautions about confusing implementation throughput, replacement cost and market value
• a second dated GitHub sample showing the repository's subsequent growth

Current-source reconciliation

The checkpoint explicitly records that:

• backend/src/Taskdeck.Api/Mcp/ProposalTools.cs still excludes approve_proposal under GP-06
• current repository guidance still requires explicit approval followed by explicit execution and keeps Preview == Apply over the latest proposal revision
• transcript triage has advanced to the LLM-backed extractor with honest deterministic degradation
• the agent-facing operating system has become more structured through the current AGENTS.md contract
• dogfooding did start, then produced a mixed outcome: the core loop was verified, while v0.1.2 was judged insufficient as a daily driver
• the old Windows first-run trilogy is resolved and the later releases supersede its recommendations

Files

• docs/analysis/2026-08-21-engineering-trajectory-checkpoint.md
  • human-readable historical checkpoint
  • explicit current/non-current reconciliation
  • durable engineering and product lessons
  • clear rules for when the artifact may and may not be used
• docs/analysis/2026-08-21-engineering-trajectory-metrics.json
  • original measured baseline
  • 2026-09-13 GitHub reconciliation and deltas
  • source-revalidation anchors and interpretation rules

Authority and scope

• Historical / non-authoritative. Current PRODUCT_DIRECTION, STATUS, REVIVAL_PLAN, live issues and release records supersede every old status statement.
• Evidence-only documentation: no runtime, schema, dependency, CI, authority or product behavior changes.
• Canonical STATUS, masterplan and test-total documents are intentionally unchanged.
• No new issue or roadmap commitment is created.

Verification

• companion JSON parsed successfully before publication
• Markdown links are repository-relative and point to existing current-main files
• both files were fetched back from the branch after creation
• no full product test suite is applicable to this docs/evidence-only change
• repository docs-governance and link checks remain required on the PR head; this connector session does not have a current executable checkout from which to run them locally

Review focus

Please check that the artifact remains unmistakably dated and non-authoritative, that the current-source corrections are accurate, and that none of the old recommendations can be mistaken for present execution order.