docs: tier the tree by lifetime, so staleness shows in the path (V-446)

Seventeen markdown files at the repo root, twelve of them dated one-shot
reports sitting next to CLAUDE.md. That is why stale docs read as
current: nothing in the path said which was which.

Root now keeps CLAUDE.md and AGENTS.md. Living docs move under docs/
and carry a Last verified line. Dated measurements move to docs/evals/
ISO-prefixed, and are never edited after the day, so a newer number is
a new file. The senior review moves to docs/archive/.

Every reference was rewritten across markdown, Go comments, the Makefile
and the recall fixture. The touched Go packages still build.

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>

CLAUDE.md

@@ -10,7 +10,7 @@ compose passes `/dev/dri` + the render gid) — the resident model stays ≤1.7B
 **Resident model:** currently **Qwen3-1.7B** (`UD-Q4_K_XL`), stock — not yet the CPT'd one.
 It replaced Qwen3.5-0.8B on 2026-07-31 because it measured better on both fixtures we have:
 67.5% vs 59.7% intent-only on the 77-case RU routing fixture, and 20/27 vs 11-17/27 on the
-talk fixture. See `MODEL-BAKEOFF-31-07-2026.md`. It is a Thinking variant, so `n_ctx` is 4096
+talk fixture. See `docs/evals/2026-07-31-model-bakeoff.md`. It is a Thinking variant, so `n_ctx` is 4096
 — reasoning tokens need the room, and 4096 is what the scores above were measured at.
 
 The **target** is still the locally CPT'd **Qwen3-1.7B** (Vikunja #122, training in flight).
@@ -25,7 +25,7 @@ Spanish. Their strong published IFEval/BFCL numbers are English-only. Model file
 `models/llm/`, so the LFM2.5 gguf sitting there is not loaded by anything. Swapping the resident
 model is a one-line change to `phraser.model_path` in `deploy/mavend.json`.
 
-See `REARCH.md` for the target architecture, `DESIGN.md` for the folded design spec, and
+See `docs/rearchitecture.md` for the target architecture, `docs/design.md` for the folded design spec, and
 `AGENTS.md` for local-preview + model-download recipes.
 
 ## Build & test
@@ -72,7 +72,7 @@ protocol; the config in `deploy/mavend.json` (with `${VAR}` env expansion from g
 
 Maven is one of four services. It owns conversation and personal memory. It does not
 own identity, operational state, or execution. Full contract in
-`MAVEN_ECOSYSTEM_ARCHITECTURE.md`.
+`docs/ecosystem.md`.
 
 ```text
 Nexus identifies.  Praxis observes.  Hexis acts.  Maven understands and coordinates.
@@ -113,7 +113,7 @@ Every cross-service call carries a correlation id minted once per action
 on in deploy** — this section used to say it was wired `nil`, which stopped being true on
 2026-07-31.
 
-- **LLM router (the intended design, REARCH.md):** the resident Qwen3-1.7B (`llmrouter.go`)
+- **LLM router (the intended design, docs/rearchitecture.md):** the resident Qwen3-1.7B (`llmrouter.go`)
   emits GBNF-constrained structured JSON, and the SAME model phrases replies. Embedder is
   demoted from a routing gate to a RAG hint. Wired at `voice.go:214` via
   `pickLLMRouter(cfg.Voice.UseLLMRouter(), llmClient)`; the flag is `voice.llm_router`
@@ -127,11 +127,11 @@ on in deploy** — this section used to say it was wired `nil`, which stopped be
 Cascade order: `stage0.go` exact-match fast-path → LLM router (when non-nil) → classifier
 fallback. Any LLM error falls through to the classifier so a turn never breaks on the model.
 
-Measured on the 77-case RU fixture (`MODEL-BAKEOFF-31-07-2026.md`): the classifier scores
+Measured on the 77-case RU fixture (`docs/evals/2026-07-31-model-bakeoff.md`): the classifier scores
 36.8% full accuracy at p50 31ms; Qwen3-1.7B scores 67.5% intent-only / 72.7% through the
 cascade at p50 ≈825ms. Accuracy roughly doubled, latency is ~27× worse, and that trade was
 accepted deliberately. **The ≈2.7s figure that stood here until 2026-08-02 was contention,
-not the model.** See `ROUTING-EVAL-31-07-2026.md` line 61, which measures the LLM router at
+not the model.** See `docs/evals/2026-07-31-routing.md` line 61, which measures the LLM router at
 p50 825ms / p95 1.2s / max 3.0s and the full cascade at p50 0.80-1.04s. Do not plan latency
 work off the bakeoff table. `Confidence: 1.0` used to be hardcoded in `llmrouter.go`, so the LLM
 path could never ask for clarification (6/6 refusal cases missed on the fixture) — Vikunja