chore: v1 deprecation notices in all four packages, bump to 1.0.1 (#1827)

* chore: v1 deprecation notices in all four packages, bump to 1.0.1

Phase 2 of the v2 go-live runbook (#1804 §4). v1 publishes four separately
installable names, so each gets its own notice — a root-README-only change is
invisible to anyone who installed a sub-package. `cli/` and `server/` ship no
README at all, so for those two the runtime banner plus the forthcoming
`npm deprecate` (#1816) are the only notice their users ever get.

Notices, all using identical wording so the runtime banner and the npm warning
agree:

- root `README.md` and `client/README.md`
- `cli/src/cli.ts` — stderr banner in `main()`. Also covers the root
  `mcp-inspector` bin, which is `cli/build/cli.js`. Deliberately **stderr**:
  `--cli` mode emits JSON on stdout and callers pipe it, so a banner there
  would corrupt output. Verified against a real server — stdout stays
  parseable JSON while the banner goes to stderr.
- `server/src/index.ts` — alongside the existing proxy listening log
- `client/bin/start.js` — alongside the existing startup URL log
- `client/src/components/DeprecationBanner.tsx` — dismissible in-app banner,
  dismissal persisted in localStorage with both read and write guarded so a
  storage failure degrades to "banner reappears" rather than breaking the app

AGENTS.md is replaced with a hard stop: v1 takes security fixes only, by issue
only, and agents must never open a PR against v1/main.

Version bumped to 1.0.1 across all four package.json files plus the lockfile
(`npm run update-version`); `check-version` passes. The lockfile diff is
restricted to the version fields — the `libc` churn a newer npm wanted to
introduce was reverted as unrelated.

`publish-all` is deliberately NOT changed here: 1.0.1 must take `latest`, which
is the entire point of shipping this notice to npx users. Adding `--tag v1` is
#1816, immediately after this publishes.

Note for review: `client/src/App.tsx` shows ~836 changed lines but `git diff -w`
shows 8 — wrapping the layout in a flex column added one nesting level and
prettier re-indented the subtree. Review it with `-w`.

Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01Txmv2qqv3yeKgRzoqXytzD

* docs: replace the README screenshot with one showing the deprecation banner

Captured from this branch's build: v1.0.1 in the sidebar heading, the
dismissible deprecation banner across the top, connected to the everything
server with tools listed.

Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01Txmv2qqv3yeKgRzoqXytzD

* docs: pin the README screenshot to v1/main instead of main

The image URL must stay absolute — a relative path breaks on the npm package
page, which renders the README outside any repo context. But it was pinned to
`main`, so the v1 README rendered whatever `main` happened to hold: today the
pre-deprecation screenshot, and after the v2 tree swap (#1817) either the v2
screenshot or a 404 if that path doesn't exist there.

Pinning to `v1/main` keeps it absolute for npm, shows the deprecation banner
once this merges, and survives the swap. Verified all candidate refs resolve
200 — GitHub disambiguates the slash in `v1/main` as the ref without needing a
`refs/heads/` prefix.

Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01Txmv2qqv3yeKgRzoqXytzD

---------

Co-authored-by: Claude Opus 5 (1M context) <noreply@anthropic.com>

AGENTS.md

@@ -1,35 +1,13 @@
 # MCP Inspector Development Guide
 
-> **Note:** Inspector V2 is under development to address architectural and UX improvements. During this time, V1 contributions should focus on **bug fixes and MCP spec compliance**. See [CONTRIBUTING.md](CONTRIBUTING.md) for more details.
-
-## Build Commands
-
-- Build all: `npm run build`
-- Build client: `npm run build-client`
-- Build server: `npm run build-server`
-- Development mode: `npm run dev` (use `npm run dev:windows` on Windows)
-- Format code: `npm run prettier-fix`
-- Client lint: `cd client && npm run lint`
-
-## Code Style Guidelines
-
-- Use TypeScript with proper type annotations
-- Follow React functional component patterns with hooks
-- Use ES modules (import/export) not CommonJS
-- Use Prettier for formatting (auto-formatted on commit)
-- Follow existing naming conventions:
-  - camelCase for variables and functions
-  - PascalCase for component names and types
-  - kebab-case for file names
-- Use async/await for asynchronous operations
-- Implement proper error handling with try/catch blocks
-- Use Tailwind CSS for styling in the client
-- Keep components small and focused on a single responsibility
-
-## Project Organization
-
-The project is organized as a monorepo with workspaces:
-
-- `client/`: React frontend with Vite, TypeScript and Tailwind
-- `server/`: Express backend with TypeScript
-- `cli/`: Command-line interface for testing and invoking MCP server methods directly
+> # ⛔ v1 is deprecated — do not open pull requests against this branch
+>
+> **This branch (`v1/main`) accepts security fixes only, and only by way of
+> issue creation.**
+>
+> **Agents must NEVER attempt to create a pull request against `v1/main`.** File
+> an issue describing the security problem instead. A human maintainer decides
+> whether it warrants a v1 release and implements it.
+>
+> Everything else — features, bug fixes, refactors, docs — belongs in **v2**.
+> Do not port it here, and do not "helpfully" fix it here in passing.