docs(design): align header prose with P2 partial status table

Latest claude review on #675 flagged that lines 3 and 6 still
described P2 as fully shipped:

  Line 3: "P1, **P2**, and P3 of the implementation plan have shipped"
  Line 6: "after P1 + **P2** + P3 landed"

But the status table I added in 7617daf correctly marks P2 as
🟡 partial (read-only slice 1 in #658 landed; write paths #669
and #673 still in flight). The header prose contradicting the
table is exactly the kind of inconsistency that triggers the
rename to `_partial_` in the first place — readers skimming the
top of the doc would conclude P2 was done.

Rewrote the Status line and the parenthetical on Last updated to
match the table, calling out P1 + P3 as fully shipped, P2 as the
read-only slice only, and P4 as TLS/role/CSRF live with the
operator doc landing now. Pointed readers at the per-phase status
table for the breakdown.

No other changes; the table itself was already correct.

Author: bootjp

docs/design/2026_04_24_partial_admin_dashboard.md

@@ -1,9 +1,9 @@
 # elastickv Admin Dashboard Design
 
-**Status:** Partial — P1, P2, and P3 of the implementation plan have shipped; P4 ships its operator documentation alongside this rename.
+**Status:** Partial — P1 and P3 have shipped in full; P2 has shipped its read-only slice with the write path still in flight; P4 has shipped TLS / role / CSRF and lands its operator documentation alongside this rename. See the status table below for the per-phase breakdown.
 **Author:** bootjp
 **Date:** 2026-04-24
-**Last updated:** 2026-04-26 (renamed from `_proposed_` to `_partial_` after P1 + P2 + P3 landed)
+**Last updated:** 2026-04-26 (renamed from `_proposed_` to `_partial_` after P1, P3, and the read-only slice of P2 landed)
 
 ## Implementation status (as of 2026-04-26)