feat: rename @adcp/client to @adcp/sdk + /client + /compliance subpaths + adcpVersion plumbing

[bokelley]

Summary

This PR delivers Stage 1 + Stage 2 of the multi-version SDK refactor. 5.22.0 minor in lockstep across both packages — fully backwards-compatible for existing consumers.

Stage 1 — package rename + subpath umbrella. Root package renamed @adcp/client → @adcp/sdk. Old name continues publishing from packages/client-shim/ as a thin re-export of @adcp/sdk. Two new SDK subpath umbrellas added: @adcp/sdk/client (alias of root) and @adcp/sdk/compliance (testing + conformance + compliance-fixtures + signing/testing). Old @adcp/client imports keep resolving via the shim; npx @adcp/client@latest keeps working via a CLI delegator. Symbol.for('@adcp/client.*') global-registry keys preserved so instanceof survives mixed-version trees. npm deprecate wired into the release workflow so the rename pointer surfaces at install time.

Stage 2 — adcpVersion constructor option (plumbing only). SingleAgentClient, AgentClient, ADCPMultiAgentClient, and createAdcpServer accept adcpVersion?: AdcpVersion | (string & {}). Default = pinned ADCP_VERSION. Each surface exposes getAdcpVersion(). Construction-time validation rejects cross-major pins (throws ConfigurationError); within major 3 every accepted pin agrees with the wire — no silent drift. Stage 3 (per-instance schema/validator selection, lift the fence, plumb wire adcp_major_version per-instance) lands in a follow-up PR.

Test plan

• npm run typecheck clean
• npm run typecheck:examples clean
• npm run build:lib clean
• npm run format:check clean
• npm run test:lib — 5355/5355 pass, 0 fail, 7 skipped
• npx changeset status --verbose confirms both packages bump 5.21.1 → 5.22.0 minor in lockstep
• node bin/adcp.js --version → @adcp/sdk@5.21.1
• ADCP_INVOKED_VIA_SHIM=1 node bin/adcp.js --version → @adcp/sdk@5.21.1 (invoked via @adcp/client compat shim)
• Workspace symlinks: node_modules/@adcp/sdk -> ../.., node_modules/@adcp/client -> ../../packages/client-shim
• test/lib/adcp-version-option.test.js — 18 new tests pass (defaults, valid pins, cross-major rejection, unparseable strings, per-surface validation)
• test/lib/compliance-umbrella.test.js — 4 new smoke tests pass (representative symbols re-export from each of the 4 source modules)

Reviewers

Run by code-reviewer + javascript-protocol-expert + dx-expert + ad-tech-protocol-expert (twice each, before and after the follow-up cleanup pass). All four cleared the change with no remaining blockers.

Migration story for downstream consumers

- npm install @adcp/client
+ npm install @adcp/sdk

- import { AdcpClient } from '@adcp/client';
+ import { AdcpClient } from '@adcp/sdk';

All subpaths (/server, /testing, /conformance, /signing, etc.) work under the new name with identical APIs. Mechanical s/@adcp\/client/@adcp\/sdk/g across imports plus the dependency swap = full migration.

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