cli/core: introduce doublezero-cli-core crate and solana_l1_rpc_url

[juan-malbeclabs]

RFC-20 implementation stack

This PR is part of a 9-PR chain delivering RFC-20: CLI standardization. Each PR's diff is only its own contribution; reviewers should consume them in order.

#	PR	Scope
1	#3753	doublezero-cli-core foundation crate + solana_l1_rpc_url
2	#3754	--solana-url + --log-verbose global flags + tracing init
3	#3755	CliContext built in main + centralized error rendering
4	#3756	rename doublezero_cli → doublezero-serviceability-cli
5	#3757	rewrite location get as the async + CliContext reference verb
6	#3758	docs/cli-standard.md + CLAUDE.md pointer
7	#3759	move per-resource subcommand wrappers into the module crate
8	#3760	add ServiceabilityCommand enum + async dispatcher
9	#3761	#[command(flatten)] + collapse binary dispatch

This PR: #3753 — position 1 of 9. Previous: (none — base is main) · Next: #3754

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Summary of Changes

• Adds doublezero-cli-core (crates/doublezero-cli-core/), the shared library crate every doublezero-<module>-cli will reuse per RFC-20. Ships CliContext + CliContextBuilder, RequirementCheck bitflags (bit values aligned with the legacy CHECK_ID_JSON | CHECK_BALANCE | CHECK_FOUNDATION_ALLOWLIST constants), the shared validators (validate_pubkey, validate_pubkey_or_code, validate_code, validate_parse_bandwidth, validate_parse_delay_ms, validate_parse_jitter_ms, validate_parse_delay_override_ms), the DisplayVec formatter, a tracing + tracing-subscriber init_logging(verbosity) helper that writes to stderr, and testing helpers (cli_context_for_tests, cli_context_default_for_tests).
• Adds solana_l1_rpc_url to doublezero-config::NetworkConfig with the per-environment defaults from RFC-20 §Environments (mainnet-beta -> Solana mainnet-beta; testnet and devnet -> Solana testnet; local -> http://localhost:8899) plus a DZ_SOLANA_RPC_URL env-var override mirroring the existing DZ_LEDGER_RPC_URL / DZ_LEDGER_WS_RPC_URL overrides.
• Migrates the shared validators.rs and formatters.rs out of smartcontract/cli/ into the new core crate. Existing import paths continue to compile via thin pub use re-export shims in smartcontract/cli/src/{validators,formatters}.rs, so the rest of the workspace is unaffected.

Diff Breakdown

Category	Files	Lines (+/-)	Net
Core logic	7	+618 / -0	+618
Tests	1	+64 / -0	+64
Scaffolding	4	+50 / -167	-117
Config/build	3	+33 / -0	+33
Generated	1	+20 / -0	+20
Docs	1	+2 / -1	+1
Total	17	+787 / -168	+619

Introduces ~620 lines of shared CLI utility code in the new core crate while shrinking smartcontract/cli by replacing its validator and formatter implementations with thin re-export shims; no behavior change.

Key files (click to expand)

• crates/doublezero-cli-core/src/context.rs - CliContext, OutputFormat, and the CliContextBuilder that resolves --env defaults from doublezero-config and applies per-field overrides.
• crates/doublezero-cli-core/src/validators.rs - shared clap value-parsers (pubkey, code, pubkey-or-code, bandwidth, delay, jitter, delay-override) with their unit tests; moved verbatim from smartcontract/cli/src/validators.rs.
• crates/doublezero-cli-core/src/requirements.rs - RequirementCheck bitflags type (KEYPAIR / BALANCE / FOUNDATION_ALLOWLIST) with bit values preserved for ABI continuity with the legacy u8 constants.
• crates/doublezero-cli-core/src/testing.rs - cli_context_for_tests() / cli_context_default_for_tests() helpers for module-crate verb tests.
• crates/doublezero-cli-core/src/formatters.rs - DisplayVec + stringify_vec moved from smartcontract/cli.
• crates/doublezero-cli-core/src/error.rs - Result alias, CliError, render_eyre helper for chain-of-causes rendering.
• crates/doublezero-cli-core/src/logging.rs - init_logging(verbosity) via tracing-subscriber with stderr writer; honors RUST_LOG when set.
• config/src/env.rs - adds solana_l1_rpc_url to NetworkConfig, wires it through per environment, and adds DZ_SOLANA_RPC_URL override plus tests.

Testing Verification

• cargo test -p doublezero-cli-core passes (16 tests across validators, requirements bitflags, context builder, testing helpers, formatters).
• cargo test -p doublezero-config passes (9 tests including two new ones covering the Solana L1 URL resolution per environment and the DZ_SOLANA_RPC_URL override).
• make rust-test green, including the program-accounts-compat run.
• make rust-lint clean.
• Verified existing smartcontract/cli consumers continue to compile against the shim files (use doublezero_cli::validators::* and friends resolve through the re-export).