ver 1.5.1 — duplicate-gate precision (common tokens, cross-kind)

Live 1.5.0 use caught the gate blocking a decision note over the single
vault-common token "echo" (min-normalized overlap gives any one-token
entity a 1.0 score). New echo_index.gate_candidates() + token_df():

- gate blocks same-kind candidates only; cross-kind name collisions
  (a decision titled after its project) warn instead of blocking
- a lone shared token blocks only when unique to that entity (df == 1);
  multi-token overlaps still block

fuzzy_candidates (advisory warnings) and exit-76/--merge-into/--force
semantics unchanged. +3 offline unit tests, gate e2e cases restructured
+2 new; verified live both directions. All suites green.

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

echo-memory.plugin.src/skills/echo-memory/SKILL.md

@@ -89,7 +89,7 @@ python3 "$ECHO" triage  --list --json                # structured inbox listing
 ```
 
 - **`capture` is the default write.** Given a title + `--kind`, it: resolves the entity via the index (create-vs-update, no manual search-first), derives the canonical path, stamps **complete** canonical frontmatter (`type/status/created/updated/tags/aliases/agent_written/source_notes` — a kind-appropriate default `status` and the kind seeded as a baseline tag, enriched by `--tags`), updates the index, **auto-links** any known entity mentioned in the body (bidirectionally), and appends today's Agent Log line — one call instead of search→put→bump→log. It also **auto-derives aliases** from the title and **learns the mention as an alias** when updating an entity under a different name. Updating an existing entity appends the **whole body** as a dated block (first line on the bullet, the rest indented under it) — nothing is truncated. `--kind` ∈ `person, company, concept, reference, meeting, project, area, semantic, episodic, working, skill, decision`. Use `--inbox` (or omit `--kind`) only when the home is genuinely unknown.
-- **Duplicate gate (create path).** When a new title strongly resembles an existing entity (fuzzy score ≥ 0.6, env `ECHO_DUP_GATE`), `capture` **stops before writing** and exits `76` with the candidate list, instead of creating a near-duplicate and warning afterwards. Resolve it deliberately: `--merge-into <slug>` routes the capture as an update to the existing entity (the new name is learned as an alias), or `--force` creates anyway after you've confirmed they're genuinely distinct. Weak resemblances still create + warn as before.
+- **Duplicate gate (create path).** When a new title strongly resembles an existing entity (fuzzy score ≥ 0.6, env `ECHO_DUP_GATE`), `capture` **stops before writing** and exits `76` with the candidate list, instead of creating a near-duplicate and warning afterwards. Two precision rules (1.5.1) keep it from over-firing: the gate only blocks on a **same-kind** candidate (a decision or meeting named after a project/person is intentional naming — those surface as warnings only), and a **single shared token blocks only when it's unique to that entity** (a vault-common word like a project family name can't gate everything that mentions it; multi-token overlaps still block). Resolve a gate stop deliberately: `--merge-into <slug>` routes the capture as an update to the existing entity (the new name is learned as an alias), or `--force` creates anyway after you've confirmed they're genuinely distinct. Weak resemblances still create + warn as before.
 - **`resolve` before constructing any path by hand** — it returns the canonical note (matching slug/title/alias, so *Bob/Robert/RS* converge) or, when nothing matches exactly, a ranked list of **`candidates`** (entities sharing a distinctive token — e.g. "echo memory" surfaces the project `echo`). Always check candidates before creating a new note; a shortened name not matching exactly is the classic way a duplicate gets made. This replaces the two-search "search-first" dance for slug-addressed notes.
 - **`recall` for "what do we know about X"** — it returns the matching notes *and* their one-hop neighbourhood (Related links, `source_notes`), so recall surfaces the web around a topic, not an isolated note. The corpus covers the entity graph **plus session logs and journal notes** (down-weighted, so entity notes win ties) — past discussions and decisions are findable even when nobody promoted them into an entity note. Ranking fuses BM25 with **freshness** (`updated:` half-life decay) and **status** (`active` boosted, `archived` demoted), and each hit prints its `updated:`/`status:` so staleness is visible. `--json` emits structured hits (`path/score/type/updated/status/excerpt`) instead of prose.
 - **`link`** when two existing notes are related but not yet connected; `capture` already auto-links what it detects.