Enable daily Pop.Standard use and exact source overloads

[serene1491]

Summary

Make the ordinary CLI path usable with the portable Pop.Standard surface and
expand the first daily-use sequence slice.

This change injects the reserved Standard Bubble into normal source and Package
builds, emits and reloads verified .poplib artifacts, and links the exact
target implementation selected from those artifacts. Portable Standard Modules
remain conventionally discovered; no compiler registry of library APIs is
introduced.

It also adds exact non-generic source function overloads. Selection uses only
arity and exact static argument types and reaches HIR/MIR as one resolved symbol;
there is no conversion ranking, result-context selection, or runtime dispatch.

Pop.Sequence gains findOr, indexOr, sumBy, productBy, minByOr,
maxByOr, append, prepend, and scan, with checked documentation, explicit
cost contracts, lazy typed adapters where applicable, and MIR/LLVM execution
coverage.

Architecture traceability

• Authorizing architecture section or ADR: ADR 0073, ADR 0074, ADR 0075, and architecture/22-public-standard-library-architecture.md
• New or changed public contract: normal CLI Bubbles receive the reserved Standard dependency; exact non-generic overload sets are statically selectable; nine portable Pop.Sequence prototypes are added
• Architecture documents, examples, or terminology updated: architecture index, type-system and base-library contracts, closed decisions, core catalog, API examples, implementation plan, roadmap, and Standard API baseline

Verification

• Tests were added or updated before implementation where behavior changed.
• Positive behavior is covered.
• Negative/rejection boundaries are covered.
• Convention, consistency, and regression coverage is present where relevant.
• Cross-backend or differential coverage is present where relevant.
• cargo fmt --all -- --check
• cargo check --workspace --all-targets
• cargo test --workspace --all-targets
• cargo clippy --workspace --all-targets -- -D warnings

If a check was not run, explain why:

All required checks ran successfully. Relative Markdown links, ADR identities,
architecture conformance, Standard baseline consistency, exact overload
reference-metadata round trips, verified artifact selection, and MIR/LLVM
Sequence execution were also checked.

Review notes

• No dynamic typing, runtime string lookup, broad reflection, or universal-table behavior was introduced.
• HIR/MIR remain backend-neutral.
• No generated artifacts, dependency caches, credentials, or editor files are included.
• This is ready for technical review.

Fully source-free registry/cache consumption is not claimed here. It remains
blocked on an accepted deterministic remapping contract for session-local Bubble
identities across independently built artifacts. The implementation deliberately
does not guess identity from filenames, namespaces, aliases, or raw numeric IDs.

The experimental C backend remains outside the parity target. The new Sequence
behavior is covered by the MIR interpreter and LLVM backend.