Follow papa-hq's research convention; the mesh links nothing

Research efforts move from status.md to 00-overview.md with active /
graduated / abandoned, matching papa-hq so the two repositories read the
same way. Playbooks, skills, README and the ledger follow.

Reverses yesterday's withdrawal of the symlink note in GENESIS. The note
was right and the withdrawal was wrong: the intent is that the mesh
creates no symlinks at all, so a founding document listing "symlinks, not
copies" as a design principle does point the opposite way from where this
is going, and that is a contradiction rather than a stale detail.

ADR 0018 records the position, proposed. ADR 0011 stays as it is — it is
the historical decision and the incident behind it is why anyone believes
either record — and is superseded in intent, not edited. Its one
editorial line, which called the wider reading false, is corrected to
state what is actually true: centralising who may link narrowed the
incident class without closing it, because a link the installer makes
resolves exactly like one made by hand.

The argument that kept linking was staleness. ADR 0004 removed it: every
managed file is already derived and reconciled, so a copy is the natural
form and a pointer into source is the shape the mesh's own model forbids
everywhere else. What is not settled, and is marked open, is how
staleness gets detected — which is the decision that makes or breaks it.

01-RESEARCH/README.md

@@ -4,12 +4,12 @@ Investigations that have not yet hardened into design.
 
 ## Structure
 
-Each effort lives in `NNN-descriptive-name/` and **must** contain `status.md`, carrying its
+Each effort lives in `NNN-descriptive-name/` and **must** contain `00-overview.md`, carrying its
 state in YAML frontmatter and a prose summary below it:
 
 ```yaml
 ---
-status: ongoing | graduated | abandoned
+status: active | graduated | abandoned
 initiated: YYYY-MM-DD
 touches: []          # design docs, subsystems or areas the effort bears on
 became: []           # required when status is terminal — what it turned into
@@ -26,7 +26,7 @@ draft designs.
 
 | status | Meaning |
 |---|---|
-| `ongoing` | Investigation in progress. |
+| `active` | Investigation in progress. |
 | `graduated` | Checked against `00-GENESIS`, decided in `adr/`, and specified in `02-DESIGN` — see `became:`. |
 | `abandoned` | Stopped or superseded. Nothing is deleted. |