one react-resizable-panels, and honest metadata for the peers

Two dependency problems, and only one of them was real.

── Real: two majors of the same library ──

The root asked for `react-resizable-panels@^4.0.15` (4.6.5) while
`src/workspaces/components` asked for `^2.1.7` (2.1.9). The workspace code targets 2.x,
whose API differs — v4 has no `PanelGroup` export, no `order` prop and no `ref` on
`Panel` — so a file that resolved the root's copy failed to typecheck in a way that
read like a broken extraction.

Nothing imported the root's version. It was vestigial, and removing it collapses the
repository to one: every importer now resolves 2.1.9 and the lockfile has zero v4
entries.

── Not real: the second React ──

Declaring react/react-dom in the package created
`src/workspaces/workspaces/node_modules/react`, which looks exactly like the
duplicate-instance bug that silently breaks hooks. It is not one. Both locations resolve
to the SAME file in bun's store — the local entry is a symlink — which I established by
resolving the specifier from each place instead of reading directory names, having
already reported it as a hazard on the strength of an `ls`.

Declared as optional peers regardless: that is the right metadata for a consumer, and it
stops bun installing peers it does not need to.

Notes corrected to match, since the wrong version of that story was written down.

tsgo clean, package 114/114, full suite 950 pass / 7 fail unchanged, frontend builds.

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

package.json

@@ -137,7 +137,6 @@
     "react-dom": "^19",
     "react-hook-form": "^7.69.0",
     "react-markdown": "^10.1.0",
-    "react-resizable-panels": "^4.0.15",
     "react-router": "^7.11.0",
     "react-spinners": "^0.17.0",
     "recharts": "3.6.0",