docs(errors): document IE072–IE090 and fill in/correct IE001–IE071

[brandonleekramer]

Summary

docs/errors.md had drifted out of date: it stopped at IE071, and many
existing entries were stubbed with TODO for their solution (and a few for
their summary). This PR brings the reference in line with the current
IndexerErrorCode enum and fills in the gaps.

All new content is grounded in the codebase — summaries come from
INDEXER_ERROR_MESSAGES in packages/indexer-common/src/errors.ts, and each
description/solution is derived from where the code is actually thrown
(packages/indexer-common/**, packages/indexer-agent/**,
packages/indexer-cli/**). Nothing was invented; where a code carries no
actionable guidance in the source, that is stated plainly rather than guessed.

Only docs/errors.md is changed.

What changed

• Added IE072–IE090 (19 new codes), matching the existing
  Summary / Description / Solution format — covering the Graph Horizon
  provision, allocation, present-POI, collect-rewards and over-allocation
  paths, plus batch-tx, subgraph-features and network-contract errors.
• Filled in TODO solutions for the many existing codes that had none,
  based on their throw sites (connectivity/DB/RPC guidance, gas/nonce handling,
  POI resolution, etc.).
• Added the missing IE037–IE040 summaries (previously blank/TODO):
  failed to query disputable allocations, query epochs, store POI disputes,
  and fetch POI disputes.
• Flagged legacy codes that are still defined in the enum but no longer
  thrown by the current codebase — the pre-TAP Scalar-Receipt, Vector-transfer,
  state-channel and query-fee-voucher flows (IE003, IE016, IE022, IE023,
  IE029–IE031, IE033, IE044–IE049, IE052–IE054, IE056) — so operators aren't
  sent chasing errors the software can't emit.
• Fixed typos and a self-referential reference (e.g. nuber → number,
  and the IE009 solution that told readers to grep for IE010).
• Restructured IE035 into a proper summary + description.

Notes for reviewers

• IE088 (Failed to present POI) is defined in the enum but is not thrown
  anywhere in the current code — the presentPOI resolver surfaces the
  underlying error, and a transaction that never mines is reported as IE089.
  It's documented as reserved and routed to IE062 / IE065 / IE089 rather
  than given a fabricated cause.
• IE090 exists in the enum (Failed to reallocate: indexer is overallocated) and is now documented as well.
• The "legacy" framing reflects two facts: these codes have no throw site in
  the current tree, and their summaries name payment mechanisms that TAP
  replaced. Happy to soften the wording to just "no longer emitted by current
  versions" if maintainers prefer to avoid the TAP attribution.

Verification

• Codes run IE001–IE090 with no gaps or duplicates.
• Every intra-doc cross-reference anchor resolves.
• No remaining TODO placeholders.