feat: enable adhoc option for prepared statement plan caching

[pimpin]

Summary

Expose the adhoc query option so callers can opt into Couchbase server-side prepared-statement plan caching (adhoc: false), while preserving the existing default behaviour (adhoc: true, no caching).

• Add DEFAULT_ADHOC = true and wire adhoc into N1ql.config so any customized config still falls back to the defaults (merge over { scan_consistency:, adhoc: })
• Thread adhoc through the reverse_merge in the n1ql-macro generated method (same pattern as scan_consistency)
• Read adhoc from N1ql.config in Relation#build_query_options, covering all relation paths (where, all, first, last, ids, update_all, delete_all)
• Per-query override on relations uses the generic with(adhoc: false) (no dedicated adhoc method)

Override priority (highest → lowest): per-call kwarg > per-n1ql-definition option > N1ql.config > default (true).

Usage

# Enable plan caching for a single macro query
N1QLTest.by_rating(key: 1, adhoc: false)

# Enable plan caching for a relation query
User.where(country: 'FR').with(adhoc: false).to_a

# Always cache the plan for a given n1ql definition
n1ql :by_stable_filter, emit_key: [:name], adhoc: false

# Change the thread-local default
CouchbaseOrm::N1ql.config(adhoc: false)

Test plan

• 3 specs in spec/n1ql_spec.rb: default adhoc: true, per-call override to false, N1ql.config override
• Relation specs in spec/relation_spec.rb: default adhoc: true, with(adhoc:) override, config override, chainability
• Run full CI: /test --fail-fast=false

CI fix

Replaced the brittle wget + apt install ./libtinfo5_6.3-2ubuntu0.1_amd64.deb steps with a single consolidated apt step that installs from the repository directly and falls back to libtinfo6 on newer Ubuntu runner images (ubuntu-24.04). This eliminates CI failures caused by Ubuntu package pool URLs becoming stale.

🤖 Generated with Claude Code

[gemini-code-assist]

Code Review

This pull request introduces support for the adhoc query option (defaulting to false to enable prepared statement plan caching) across Couchbase ORM N1QL queries and relations, along with corresponding tests. The review feedback highlights a potential issue where custom configurations might omit the adhoc key, resulting in it resolving to nil and silently disabling plan caching; merging the custom configuration with the defaults is recommended to prevent this.

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[pimpin]

Some more fix todo.