Move expiring-shapes log counts into Logger metadata

[erik-the-implementer]

Summary

Replace the interpolated number_to_expire/max_shapes values in the Logger.notice(\"Expiring #{n} shapes as the number of shapes has exceeded the limit (#{max})\") call with a static message plus those values as structured Logger metadata. Extends the OTEL log handler's metadata_map so the counts surface as shape.expiry.number_to_expire and shape.expiry.max_shapes attributes.

Why

The expiring-shapes notice fires frequently and every entry currently contains different counts, which prevents log aggregators from grouping them together and makes filtering/aggregation in Honeycomb awkward. Following the pattern in #4145, keeping the message text static (with the dynamic values exported as attributes) makes these events easier to search, group, and alert on.

Refs electric-sql/alco-agent-tasks#33.

Test plan

• mix compile --warnings-as-errors passes in packages/sync-service

[claude]

Claude Code Review

Summary

This PR converts the expiring-shapes Logger.notice call from a string-interpolated message to a static message with number_to_expire and max_shapes as structured Logger metadata, and wires those keys into the OTEL log handler's metadata_map so they surface as shape.expiry.* attributes in Honeycomb. The change is minimal, correct, and follows the established pattern from #4145.

What's Working Well

• Consistent pattern: Exactly mirrors the approach used in Move shape_handle into Logger metadata for No-consumer error #4145 for other log metadata — using Logger.notice/2 with a keyword-list second argument is idiomatic Elixir and correct.
• Clean OTEL wiring: The two new entries in runtime.exs's metadata_map are correctly scoped (shape.expiry.number_to_expire, shape.expiry.max_shapes) and placed in the right block.
• Changeset present: The .changeset/fix-expiry-manager-log-attributes.md is included, describes the change accurately, and is categorized correctly as a patch.
• No behaviour change: The expiry logic itself is untouched; only the log formatting changes.

Issues Found

Critical (Must Fix)

None.

Important (Should Fix)

None.

Suggestions (Nice to Have)

• Log message still readable without metadata: The static string "Expiring shapes as the number of shapes has exceeded the limit" is unambiguous even when viewed in a plain-text log stream, since the counts appear in the structured metadata. No action needed — just noting this tradeoff is already handled well.

Issue Conformance

The PR references electric-sql/alco-agent-tasks#33, which appears to be an internal/private task tracker rather than a public GitHub issue. The PR description compensates for this with a clear ## Why section explaining the aggregation/Honeycomb motivation, so reviewers have full context. No gaps in the implementation relative to what's described.

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Review iteration: 1 | 2026-04-24

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 68.08%. Comparing base (3cef0ca) to head (a788273).
✅ All tests successful. No failed tests found.

Additional details and impacted files

@@           Coverage Diff           @@
##             main    #4161   +/-   ##
=======================================
  Coverage   68.08%   68.08%           
=======================================
  Files         130      130           
  Lines       16211    16211           
  Branches     3912     3911    -1     
=======================================
  Hits        11037    11037           
  Misses       5170     5170           
  Partials        4        4           

Flag	Coverage Δ
packages/agents	38.39% <ø> (ø)
packages/agents-runtime	81.34% <ø> (ø)
packages/agents-server	65.55% <ø> (ø)
packages/agents-server-ui	0.00% <ø> (ø)
packages/electric-ax	30.46% <ø> (ø)
packages/experimental	87.73% <ø> (ø)
packages/react-hooks	86.48% <ø> (ø)
packages/start	82.83% <ø> (ø)
packages/typescript-client	94.30% <ø> (ø)
packages/y-electric	56.05% <ø> (ø)
typescript	68.08% <ø> (ø)
unit-tests	68.08% <ø> (ø)

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