feat(cli): --json parity for 9 remaining read commands (X4)

[NagyVikt]

Summary

Extends Theme N3's --json envelope to every remaining read-shaped command per Theme X4: config, daemon --once, forecast, savings, hero, export, import, parallel --list, kiro (no args).

• BaseCommand subclasses opt in via ...BaseCommand.jsonFlag and emit through emit().
• Validation errors converted from this.error(...) to thrown AuthmuxError subclasses so they fall through to the structured handler (preserves human-mode wording).
• parallel and kiro intentionally bypass BaseCommand per 01-ARCHITECTURE.md §1.3 (no Codex registry coupling); they wire --json manually via writeJsonEnvelope. Wire shape is identical.
• daemon --watch --json is rejected with a structured error and deferred to Theme X3 (streaming observability). Only --once gets --json today.

Exit criteria (Theme X4)

• Every read command has --json. (9 commands listed above.)
• A snapshot test asserts every --json output is valid JSON for at least one fixture per command (src/tests/json-parity.test.ts).
• docs/future/02-COMMANDS.md lists the JSON schema for each command.

Commands converted

Command	Example success envelope
config <section> [action]	{ok:true,data:{section,action,status:{...}}}
daemon --once	{ok:true,data:{switched:false,reason:"auto-switch is disabled"}}
forecast	{ok:true,data:{accounts:[{name,score,circuitState,tokensAvailable,usable}]}}
savings	{ok:true,data:{totalSwitches,autoSwitches,...,autoSwitchRatePercent}}
hero	{ok:true,data:{sections:[{title,items:[{command,description}]}]}}
export [dir]	{ok:true,data:{exported,targetDir,files}}
import <path>	`{ok:true,data:{mode:"file"
parallel --list	{ok:true,data:{action:"list",profiles:[{name,configDir}]}}
kiro	{ok:true,data:{action:"list",accounts,active,dataDir}}

Verification

npm run build          # clean
npm test               # 138/138 pass (129 prior + 9 new)

Test plan

• Build is clean (npm run build).
• Full test suite green (138/138).
• Each --json command produces exactly one valid JSON document on stdout (snapshot test).
• Validation errors emit {ok:false,error:{...}} envelopes (verified for config auto, export, import, daemon --watch --json).
• Human-mode output for every converted command unchanged (e.g. authmux hero still renders ANSI tutorial, authmux savings still prints the multi-line report).

Conflict notes

Touches BaseCommand-using commands; X1 (createApp factory) will refactor BaseCommand itself, so a small rebase is expected when X1 lands. X3 may also touch BaseCommand. No overlap with X2.

🤖 Generated with Claude Code