Show task subjects in task updates

[OllieinCanada]

Closes #988

Problem

Claude TaskUpdate messages only carry a task ID. Roast therefore renders output such as:

TASKUPDATE #1 → completed

The useful subject is available earlier, when the matching TaskCreate call and result establish the numeric task ID.

Fix

• remember successful TaskCreate ID-to-subject associations in the existing per-invocation Claude context
• render later task updates with the known, quoted subject
• preserve the current #id output when the create result is missing, failed, or has an unexpected shape
• truncate long subjects using the formatter's existing limit and escape quoted subjects

The state remains local to one Claude invocation; there is no global cache or provider behavior change.

Evidence

The regression test failed on current main before the production change:

Expected ... to include "TASKUPDATE \"Read full code\" → completed\n".
Actual: "TASKUPDATE #1 → completed\n"

After the fix:

• Claude invocation tests: 49 runs, 88 assertions, 0 failures
• Claude tool-use formatter tests: 55 runs, 62 assertions, 0 failures
• bundle exec rake sorbet: no errors
• bundle exec rake rubocop_ci: 156 files, no offenses
• bundle exec rake test: 1,240 runs, 2,166 assertions, 0 failures, 0 errors, 0 skips
• git diff --check: passes

All tests ran deterministically on Ruby 3.4/Linux without an LLM or external model API call.

AI assistance

Implementation and test drafting were AI-assisted. I reviewed the resulting diff and verified it with the repository's complete CI command set.