chore(release): v0.6.0 — U6, benches

The sixth of seven v1 units. A bench is a running thing, registered: identity
is the normalized URL so re-posting updates the row instead of appending a
fifth, `booth link` refuses the one shape that now has a better home, and the
board marks the rows whose booths are gone without deleting a single one.

Minor rather than patch, approved by the operator. Two capabilities arrived and
one verb changed behaviour for seventeen agent handles, which is the
push-notification bar in the tier test: `booth bench` is new, the board gained
a dead marker, and `booth link` now refuses a booth URL and a credentialed one.

444 -> 607 tests across the unit and its three cold gates. All four review
gates closed: an in-session seam review (three real contract defects, including
one that would have 404'd the whole board page), an in-session adversarial pass
(four defects, one of them this repo's own FIFO lesson recurring in a new
file), and three cold cross-frontier panels -- contract paraphrase, code-vs-
contract, and a diff-scoped bug hunt -- folded in full with exactly one finding
declined and its reasoning recorded.

Measured before contracted, and the measurement changed the unit: the design
doc's headline 69% rot was two defects wearing one number, and U5 had already
closed the larger half. Identity is the FULL normalized URL rather than the
origin because origin identity merges eight distinct gitea repositories, three
unrelated model cards, and the two LRPG surfaces the design doc itself names as
an example of two real benches.

ROADMAP.md

@@ -1,7 +1,7 @@
 # The Booth — roadmap
 
 Design: [`docs/design/information-architecture.md`](docs/design/information-architecture.md).
-Current version: `0.5.0` (U1 through U6 landed; extracted from eshpfi 2026-09-21).
+Current version: `0.6.0` (U1 through U6 landed; extracted from eshpfi 2026-09-21).
 
 ## v1 target
 
@@ -15,7 +15,7 @@ defect — not a wish. The measurements are in the IA doc.
 | 3 | ~~**Declared embed seam**~~ — **landed `87e2c53`, released `v0.5.0`** | 6 regexes injected into arbitrary author HTML, load-bearing for asks | U3 |
 | 4 | ~~**Derived lifetime**~~ — **landed `c3a97c1`, released `v0.4.0`** | 70% of booths on the `.forever` escape hatch (54% when first counted) | U4 |
 | 5 | ~~**Self-announcing booths**~~ — **landed `c015a91`, released `v0.3.0`** | job 5 had no home, so it lived on the link board as 145 dead rows | U5 |
-| 6 | ~~**Benches**~~ — registry, identity, enforced rule, migration | 69% link-board rot; the same bench posted 5× | U6 |
+| 6 | ~~**Benches**~~ — **landed `1c3ce5d`, released `v0.6.0`** | 69% link-board rot (re-measured: 178 booth rows + 8 bench re-posts) | U6 |
 | 7 | **Navigation at 270 items** — sections, rail, filters, grid keyboard | one flat wall; subfolder structure discarded at render | U7 |
 
 Ordering is dependency-driven, not priority-driven: **U1 → U2 → {U3, U4, U5} →