Make the router's routing state authoritative instead of sniffed

[GoodForOneFare]

Bug

StdoutRouter.disable restored the original write method but left the write_without_cli_ui compatibility method installed. Because enabled? inferred routing from that method, the process could reach a contradictory state:

• routing was inactive,
• enabled? still returned true,
• enable refused to route the stream again,
• Capture#run accepted the false-positive state and silently captured nothing.

Resolving enable/disable only through the current $stdout and $stderr also orphaned routes when either global was replaced. with_enabled compounded the problem by unconditionally disabling on exit, including routes that existed before entering its scope.

Fix

Routing state now lives in a weak identity registry rather than being inferred from methods installed on a stream.

• Routing membership is explicit. routed?(stream) checks the registry, enabled? remains as a compatibility alias, and routed_streams returns a read-only snapshot for inspection.
• enable is additive and per-stream. It routes the current $stdout and $stderr without discarding routes temporarily displaced from those globals. disable(stream) removes one route; no-argument disable drains every live registered route.
• Scoped activation unwinds only its own work. with_enabled remembers only streams it newly routed and removes only those on exit. If a later stream fails to activate, activation rolls back only streams added by that attempt and preserves pre-existing routes.
• Capture establishes the routing it needs. Capture#run executes inside with_enabled, so disabled, half-routed, or partially replaced stdout/stderr globals are routed for the capture and restored afterward instead of raising or letting output escape.
• The registry does not retain abandoned caller-owned streams. Active routes are held in an ObjectSpace::WeakMap; callers should still pair explicit enable/disable operations, but dropping a transient stream no longer pins it for the process lifetime.
• The compatibility bypass remains a real bypass. The router-installed write_without_cli_ui closes over the stream's pre-routing write. write_without_routing uses the same method when available, so a later write wrapper can call either bypass without re-entering itself.
• Independent cli-ui copies do not stack routers. A stream-owned ownership record distinguishes this router's permanent compatibility method from a foreign one. Activation preflights all current streams and benignly declines before changing anything if another copy already owns one.
• Writer requires the pre-routing method explicitly. This prevents accidentally constructing a Writer around an already-routed write, preserves pre-existing singleton wrappers during normal disable, and lets in-flight writes finish after deactivation.
• Temporary test streams use scoped routing. Tests that replace stdio with capture_io use with_enabled, avoiding accidental long-lived routes.

The earlier role-retagging and exact routing-state restoration layer was removed. Routing is additive and idempotent; scopes need only remember the streams they added, not rewrite the roles or wrappers of existing routes.

Tests

Coverage includes:

• enable → disable → GC → re-enable,
• transient and permanent $stdout/$stderr replacement,
• aliased stdout/stderr,
• targeted and global disable,
• nested/scoped activation and failure rollback,
• capture while disabled or partially routed,
• compatibility and public bypasses called by later write wrappers,
• foreign compatibility markers and duplicate-router hook prevention,
• weak-registry collection of abandoned streams,
• public routing inspection without mutable registry access,
• pre-existing singleton write restoration,
• in-flight writes and direct bypass behavior.

Validation:

• 156 tests and 509 assertions across seeds 630, 20260817, and 8675309, with one existing skip,
• RuboCop clean,
• Sorbet clean.

🤖 Generated with LLM assistance

(posted by an LLM bot on behalf of Gord)