feat(planner): add --rename and --slug naming overrides

[dadachi]

What

Implements the ROADMAP "Optional explicit naming overrides" feature — flag-based, no interactive prompts (scriptable + CI/MCP-safe, per ROADMAP.md line 83). Lets a human veto the planner's noun/name choices without taking over the whole DomainSpec.

--rename From=To (repeatable)

Overrides one of the planner's domain rename targets. Keyed on the substrate token (Shop / Shopkeeper / ItemTag); semantics are "change a planned target" — an override matching no planned rename is reported and dropped, never silently added.

--slug=<kebab>

Overrides the planner's slug, which drives the project name (NativeAppTemplate → VetClinic / …Api / …App) across all three platforms, plus the output dir out/<slug>/, DB prefix, and env-bridge token. Invalid kebab-case is reported and ignored.

npx nativeapptemplate-agent "a vet clinic queue" --slug=vet-clinic --rename Shopkeeper=Provider
#  project: VetClinic (slug vet-clinic, output out/vet-clinic/)
#  override: Shopkeeper → Provider (overrode planner's "Vet")

How

Both overrides apply right after the planner in dispatch(), before the env-bridge/workers/reviewer/judge/report read domain, so every downstream consumer sees the final plan. Both are exposed on the CLI and the MCP generate_app tool.

File	Change
src/rename-overrides.ts (new)	pure parseRenamePair + applyRenameOverrides
src/slug.ts	isValidSlug (mirrors the planner's slug contract)
src/dispatch.ts	DispatchOptions.renameOverrides + slug, applied + traced; renameOverrideOutcomes on the result
src/index.ts	--rename / --slug parsing, confirmations, warnings, usage
src/mcp.ts	renameOverrides + slug params on generate_app
README.md, ROADMAP.md	naming-flags table + status note

Testing

• npm run build clean (strict, exactOptionalPropertyTypes).
• npm run test → 68/68 pass (13 new: arg parsing, merge semantics, slug validation, end-to-end dispatch for both flags).
• CLI smoke (stub mode): changed-target / unmatched-with-hint / malformed for --rename; valid / invalid-fallback for --slug; both together.

Notes / deliberate scope

• --slug couples the project name to the output dir + DB prefix (one coherent rename) — the chosen behavior. A decoupled --project-name (dir ≠ code name) was considered, not built.
• displayName override remains deferred.
• No reserved-token guarding on override targets (e.g. --rename Shop=Task could shadow Swift's Task); these are explicit escape hatches, same as the planner's existing trust boundary. Can add a guard if wanted.

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