[martinconic]

Checklist

• I have read the coding guide.
• My change requires a documentation update, and I have done it.
• I have added tests to cover my changes.
• I have added or updated fuzz targets for any code handling untrusted input. (Not applicable: operator configuration only.)
• I have filled out the description and linked the related issues.

Description

Closes #5689. Follow-up to #5596, proposed by @gacevicljubisa there.

Bootnodes can now be configured with node-mode: bootnode instead of node-mode: full plus the separate bootnode-mode option. Like #5596, this changes configuration only: node-mode: bootnode resolves to exactly the node that full-node: true + bootnode-mode: true gives today (full mode with bootnode mode set), so nothing changes on the network. No code under pkg/ changes; /node keeps reporting beeMode: full for bootnodes.

node-mode: bootnode

• Requires a blockchain RPC endpoint, as full mode does ("bootnode requires blockchain-rpc-endpoint to be set").
• Implies no swap, chequebook or storage incentives. Swap starts only when swap-enable: true is set, and chequebook follows swap, as for bootnodes today.
• storage-incentives-enable: true is accepted with a warning that it has no effect on a bootnode. reserve-capacity-doubling is passed through unchanged, as today: it is not unused on a bootnode (NewBee range-checks it, derives the push-sync receipt tolerance from it and passes it to staking).
• The value is matched case-insensitively. An explicit bootnode-mode: false is overridden, with a warning.

bootnode-mode is deprecated, not removed.

• Without node-mode (legacy), full-node: true + bootnode-mode: true keeps working. The migration warning now reports node_mode=bootnode and lists set=[node-mode=bootnode], remove=[full-node, bootnode-mode].
• node-mode: full + bootnode-mode: true keeps working as a bootnode and logs that bootnode-mode is deprecated in favor of node-mode: bootnode.
• The --bootnode-mode flag is marked deprecated, like --full-node.
• "boot node must be started as a full node" now adds "use node-mode: bootnode".

Packaging: the four bee.yaml variants, the Docker env template and the Docker README document bootnode, mark bootnode-mode deprecated, and list bootnodes under the RPC requirement.

Motivation and Context

A bootnode is effectively its own mode: full mode exempts it from the options it implies, and bootnode-mode is only valid together with full mode. Making it a node-mode value lets operators say what they run in one option. Landing it before the release that ships node-mode avoids migrating bootnode configs twice (first to node-mode: full + bootnode-mode, then to node-mode: bootnode).

Related Issue

• Make bootnode a node-mode value (node-mode: bootnode) #5689 (scoped to configuration; protocol behavior of bootnodes is out of scope)
• refactor: node mode two regimes #5596
• fix(config): disable options rejected by bee in light and ultra-light… beekeeper#621: bootnode profiles keep working as node-mode: full + bootnode-mode: true (with the deprecation warning) and can move to node-mode: bootnode as a follow-up.

Test plan

• TestResolveNodeMode and TestResolveNodeModeWithBoundFlags cover node-mode: bootnode: implied defaults, case-insensitive value, missing RPC endpoint, swap with chequebook following it, chequebook without swap rejected, verification without swap, explicit bootnode-mode: false, storage incentives and reserve doubling.
• TestResolveNodeModeWarnings asserts the deprecation warning for node-mode: full + bootnode-mode, the bootnode warnings, and the legacy migration (node_mode=bootnode, set/remove lists).
• TestNodeModeBootnodeMatchesFullBootnode resolves node-mode: bootnode and node-mode: full + bootnode-mode: true over every combination of RPC, swap, chequebook, incentives, verification and reserve doubling (216) and requires identical results or identical errors.
• TestLegacyMigrationPreservesBehavior now also varies bootnode-mode (unset, true, false) and reserve-capacity-doubling: across 1944 legacy combinations, every config that starts (504) runs the same after applying the migration warning, and the rejected ones match the pre-node-mode rules.
• Each new rule was broken on purpose and caught by these tests.
• Resolver outcomes compared against master over 1080 configs: only node-mode: bootnode rows change (previously an invalid value); 168 other rows change only their error message (the two improved bootnode messages).
• Config file (flat and nested blockchain-rpc keys) and BEE_* environment variables checked through the real config pipeline; bee start smoke tests with node-mode: bootnode, the deprecated alias and a legacy bootnode.
• go vet ./..., golangci-lint v2.15.0 (0 issues), make build, make check-whitespace and make test pass.

AI Disclosure

• This PR contains code that has been generated by an LLM.
• I have reviewed the AI generated code thoroughly.
• I possess the technical expertise to responsibly review the code generated in this PR.